I see.  I don't know the answer to that question but I do think you can set some clear boundaries for yourself and indicators to look for in his behavior (not his words, I think) to help you decide whether there is reason for hope.

Me88, it sounds to me like you get a lot of your sense of self and validation from being wanted or needed or seen positively by other people. That's wonderful, because it's right to want to help other people and make their lives brighter, but it also creates a vulnerability. Borderlines are expert at telling us how acutely, truly, madly, deeply they "need" us, and then yanking this affirmation away in the most abrupt and violent fashion, leaving us traumatised and lost.

When you imagine a big positive life change, what comes to mind?

This is so much.  I relate to the guilt and the worry and the loss and sorrow and the exhaustion.  I suspect you may not even be aware of how much you need the separation, how much better you'll feel with some time and how much clearer things will be. Take care.

He has started medication. And since that night, he has seemed more serious than I've ever seen about wanting to get better. About wanting to be in therapy. I told him that I would need time, space and a lot of repair and reassurance if we were to ever try again. If that is too much to ask then yes, i will have to fully move on for my own health.
Am i wrong for having hope that he will commit to healing?

A question I have is "What has really changed?"  You slept with him, but you seem to know that there's no future there and you should pick yourself up and get back to NC.  Or am I wrong?  Did something change?

Feeling remorse is good for helping us do differently in the future, but making our imperfect human selves crazy with guilt or confusion is not so helpful I think.   

Recently, I found myself despairing about how sad I was and a friend told me, "It's ok to be sad."  It got me thinking about all the awful realities people have to carry around with them.  I wish it wasn't that way but it is.  And it seems that just "accepting" that fact took some of the sadness away from me.  I'm less sad overall and I'm less sad about being sad.  I also know that grief doesn't leave you, but it does get less frequent (and sometimes less intense), and that's improvement, I'd say.

I sympathize and empathize and hope you can find a path forward.

Jackie40, that is definitely familiar.  Interestingly, I see some small recovery from that now happening as part of my larger movement to focus on taking care of myself -- recognizing not only that that's all I can control, but that I have a right to do it.

And the truth is, even if our parents were not as fair as they might have been (not saying they weren't, but even if), that is not our fault and it certainly can't be changed now.  We all have to deal with the hand we've been dealt -- with compassion for ourselves and for others, of course -- but it is what it is.

First of all, consider: what do you want?  To continue caretaking her?  I assume the status quo isn't working for you, or you wouldn't be here.  Do you want to find a way to leave her and find someone who could consider your own needs as well as her own?  Do you just want to find a better way to continue to live with her? 

It's okay to feel physical desire for someone (it sounds like that's all this was for you, since you're talking about her appearance).  Just keep some mental perspective on why it wouldn't be what you're expecting it could be again.  Use your brain to keep your body in check, and don't beat yourself up about your feelings; consider why you're having them and realize we're all human, and you're not a loser for having them.

If missing her after nearly 2 years makes you an idiot then I dread to think what I am, as I still miss and think about my BPDex from 38 years ago

I didn't think about her that much for most of my life since our final breakup, but this past 5 year she really has come back into my mind big time. Maybe it's because I'm a lot older now and am thinking the 'what might have been' part of my past life. The fact she lives only 2 miles from me doesn't help either.

We'll never truly forget them because our relationship with them was unlike any other. The good times we did have with them can come back and trigger us at any time.. a memory, a song, etc.

Sadly, the human brain has no 'delete' option, just a 'file right at the back of the cabinet and try not to open the cabinet' option. It's the best we're going to get.