It's become so normal i don't Want to let go

[Skog]

Hey, first post, so hopefuly all good and formatted and stuffs

Trigger warning for minor self harm- hope i'm doing this right

I came here to just try and do more research, because i still want to help her- let's call her 'C' for now
but
she was open about having BPD when we met 8 months ago, but she was alwasy cagey about details, and to be honets, what i knew about it couldn't cover a folded napkin, i've learned lots since, but it's brought to light that my previous psuedo partner 'B' and my ex wife 'A' exhibited traits too, to greater or lesser extents
Anyway
I'll try to cover to my situation here briefly
It's deeply ingrained into me to help people around me and to not expect much if anything in return- Doing The Right Thing, for little or sometimes even negative gain, other than knowing i've Done the Right Thing- like moving odd bits of wreckage or the like out of the road if i'm walking- wouldn't want someone to hit that or have it hit a pedestrian

When C first got mad at me for no obvious reason, i didn't even register it, i can't even remember what it was, but it was so irrational that i just shrugged it off and kept making us breakfast- she'd had me basically move in with her early on- i think within the first month i was staying over most nights, then she'd say "ooh make sure you bring this" or " you need clean clothes here" and it was so nice and wholesome, i'd been very lonely after my wife had left and i'd had to give up my cats, so it was godsend that there was this amazing fun lady that just Wanted me- she'd just moved to the area and was looking for work so we had lots of time together while she was job hunting.
Once she'd gotten a job i was trying to be a bit more structured (i'm self employed so as long as the work get's done the timescale isn't toooooo important) I'd wake up first, make breakfast for us, make her a coffee and sort the dishwasher- we'd get the bus to her work, i'd drop her off and then go back across town to my place so i could work, then meet her again after work, and then cook her dinner, watch some TV and go to bed, Really comfy but not the most enthralling evenings.
Due to her past though, certain things were more difficult- the fireworks that frequent this area, even outside of bonfire night and new years always spooked her- this was the main impetus for having me there, so i could help her if she had a PTSD episode- i got quite good at defusing those, but one of the big fights that resulted was when i answered a call when i thought she was good after one, and she wasn't- suddenly i'm the worst person in the world, but, and this is the part that always hurt me the most, she'd never say up front, always a day or 2 later and always via text
she was very variable about intimacy as well, some days she'd be all over me, others she'd act like i was a stranger suddenly in her bed, one time i'd asked if i could take a picture of her because she just looked so good that day, with her phone- that was always my system, so he has the picture and can send it to me if she wants to, which she did.
The next day (I think) while i was making dinner she came into the kitchen and took my clothes off because "See how you like being vulnerable" i didn't quite get it at the time and she did like my body so i just kept cooking, as you do when something weird happens but the food is already part cooked, later she just acted like nothing happened- stuff like this went on for a bit until she had a massive go at me at the end of november and said she'd broken up with me
She spent the next week or so asking me to help her out with stuff as she was ill, and then asked me to stay around again (the last time) at which point she said that she wouldn't be doing good over the holidays as she has too many bad memories, so i might not hear from her until the new year, but things were good- since then it's only gotten worse and every plan or promise has fallen through, until she'd SH'd a few weeks ago, and asked me to help as she couldn't reach properly to check it was okay, and then the next few days she asked me to drop by or help her out with things, and mainly massaging her as she was really tense- the first time it had been raining and she'd said it was fine to take most of my clothes off so i wouldn't get her sofa wet/ dirty and she had all but her knickers off to facilitate the massage- after sorting lots of tension she spent a good 20 minutes just cuddled up to me like she used to, it felt so good after everything that had happened and she seemed fine with basically everything other than me touching her labia when i was working on her, this happened a couple more times and as she seemed Very into it and me , so i was a little bold and to facilitate things had taken off her remaining clothes, no issue at the time other than a "really?" but she was fine and as soon as i got to work on her pelvis it was like she melted- after this we cuddled a little and then she had me help with some chores while she had a shower,then helped make her bed- she remained nude the whole time and seemed unphased by it, as she'd said, nothing i'd not seen before, but to be clear nothing sexual occured
a couple of days later i got some of the worst messages i've ever gotten from her calling me all sorts of things and accusing me of other things, but crucially, some things i Had done, so instead of trying to just ignore the outbust, i did my best to applogise and that just made things worse, we talked at cross purposes for a bit but the last message i got from her was her saying she had a GF now and that i should leave her alone
But she's still on dating apps, (i had been since Januray as she'd said it'd be a year or more before she dated again and i shouldn't wait for her to get better, and i was still unsure of what to do at that point) but i saw her on one today and i just can't leave it alone, i know she's bad for me, but i want to help her , because it's the right thing to do, and she can be very grateful for it, even if the gratitude is fleeting and the togetherness gestures were hollow- we'd met each others families, we'd lived together for a few months and she'd given me a promise ring early on as she was that comitted to me- this was only a few months after the divorce was finalised and that had meant a lot to me, probably too much, but it was nicer than the one my ex wife had gotten me for the wedding
I've probably written far too much but this seemed like the imporant bits
I know i should let her go because she's so bad for me, but she seems to keep wanting me around (at her convenience) and i don't like to quit on people, especially if they've told me so much to tell me Why, and with everything i've read on the subject i can try and work around the episodes, but she can be Nasty when she wants to be

I know what i should do, but this is so much harder as every relationship i've had has been better in some way and this last one was the best, but it's also been the worst
The lady i fancied (B) and who'd fancied me had been very similar, but without dating tying things together it was easier to let go
My ex wife (A) looking back was quite similar too, but as even after the wedding we'd had to stay long distance i'd only see her for maybe 6 months in the year while she was in the states, so lots of stuff sort of didn't happen.
What i'm trying to say is i'm just so used to this now that the last Healthy relationship i had was nearly 10 years ago and that ended badly. i don't know how to change things to get away from it- i've tried but the familiar is comfy, even if it hurts

[Skog]

Sorry this was really wordy but i tried to chop it down but leaving in anything important or contextual and that's what i ended up with, it's all conflicting situations, like the texts are from a totally different person- i dreaded the sound of her text tone so much i changed it back to the regular in the hopes of just ignoring it, but i Want to hear from her, becasue sometimes it's good and she can be so sweet, Sometimes