Okay. Things have improved. My fiance and I feel a lot closer right now. I believe him a lot more when he says he loves me and I'm important to him. I told him how I felt like he was treating her in a way that he used to treat me, but wasn't anymore. And that he was chronically unhappy with me. And we talked...
And then GF came over and was feeling very sad and vulnerable herself, and I felt sort of intensely empathetic and caring towards her, and then I suddenly felt the thing between the three of us to be less threatening. :-)
I think my fiance does feel like a caretaker sometimes. But probably not in quite the way you imagine. Most people who see me think I'm totally normal. Not quite true, but I feel well enough (and have acquired enough skills) to affect "normal". But I do have these periodic decompensations, where things get really bad really quick. And I need him badly then.