Hello Lovemyjess,
Welcome to the bpdfamily!

You have shared a compelling story. I think it's great you reached out to a therapist, and I completely understand the insatiable need to read and learn about BPD. For me it's been 8 months since I finally realized what BPD was, and I'm still reading and learning about it, albeit at a slower pace. It's such a relief to understand that there is a complexity to the pwBPD that we were always clueless to, right? That the person who always made us feel like everything we did, no matter how much we did or how great the deeds, was always giving us the message that we weren't doing enough, or doing it right, and that we didn't love them enough, or we should do more to prove it! To understand that all that "stuff" was distorted thinking on
their part, and NOT our fault (despite what our mother was telling us), what a relief! Suddenly we could accept that maybe we didn't
have to feel FOG all the time, because it
wasn't all our fault. The tricky part is to unlearn the feelings of FOG after a lifetime of feeling them.
For me, when I was at the beginning of this journey of understanding of my uBPD mom's disease, I still tried to rationalize her behavior after everything I had done for her. I was so hurt. I didn't understand any of it. Her behaviors were so irrational, and mean, and not at all in keeping with how hard I tried to support her. I just kept replaying in my mind everything I had done, and what my sacrifices were to do those things. I was filled with resentment. I'm not sure if you might be experiencing some of these things too. It's hard to look back and pinpoint what turned the corner for me. I think I finally hit the wall with her, because it felt too insane and impossible. Then it finally hit me: she was going to do and say what she was going to do and say. I couldn't change that. The only thing I could change was how I was going to react to it. That was the ONLY thing I had any control over. Then my real journey began, because I realized it was me I had to change, which also meant I had to figure out what my role in the insanity was, and stop contributing to it. Eight months later, I still have a relationship with my mom, she's still difficult to impossible (but I've accepted that's never going to change), but I've learned how to manage myself and my interactions with her. It's made a big difference.
You reference your "poor husband". I feel bad for my H too. He attends T with me because I invited him along. I felt he would grasp things better if he heard T with
his own ears. And because he's learned about BPD too, he is a great sounding board when I'm trying to figure out how a "normal" person would respond to some of my mom's attention seeking behavior, and negative "daggers" at me. She hasn't stopped trying to draw me in to drama, I've just stopped getting sucked into it. I have worked hard to not play into that any more, and I feel I'm making progress with it.
Your story is pretty heavy hitting, and you've clearly put amazing effort into helping your mother, at your own expense. Know that it isn't your fault. Nothing you could have done differently with your mom, would have led to a different ending. All paths lead to the same finish line with BPD, unless we "nons" can figure out how to "work with it". Even then, some cases are so toxic, that NC is the only route for some people. I've kind of developed the theory that the BPD disease leads us "nons" to the point where we have to come to our own reckoning, and figure out what to do to save ourselves.
I dreaded every relationship of her ending because I knew I’d have to fix it
Fix the relationship or fix
her? Why you? Why not her? Our mothers have unknowingly groomed us to care for their emotions and feel their feelings for them. When I realized this (thanks to someone on this site pointing it out to me), I started working on separating my emotions from my mothers, and allowing myself to feel my own emotions, and let her feel hers, and soothe herself. You probably won't believe this, but if you give the BPD enough time and space, they really can soothe themselves. But they don't do it willingly. They're going to push back by pushing every button of yours to FOG you. We have to hold our boundaries. It's kind of like training kids and dogs (said with a lot of humour)

After the "extinction burst", it gets better. I've also learned I can't solve her problems, despite desperately wanting to help her, and prevent her from crashing. Sometimes they have to figure it out via the old fashioned "school of hard knocks".
my therapist told me I am feeding her illness by continually calling her back and apologizing.
Your therapist is right. When you apologise, you are "validating the invalid". Not helpful.
After years of trying to research what was happening and why I felt such anxiety with my mom, I finally had an answer! I was so relieved.
yes!

I feel like I am betraying her by writing this
You are not. Those might be your mother's feelings if she knew you were posting here, but what she doesn't know doesn't hurt her, right? Instead, posting here helps you. That's the
other side of the coin, right? Maybe this is the right time to start separating your mother's feelings from your own. Maybe by writing this, you are investing in some much needed self-care for yourself. That is important, and definitely the right thing to do, and the right side of the coin for you.
Let us know how we can help.