Welcome to our forum.
You have a complex set of symptoms, and would do well if you could find a poly-friendly counselor and meet with them quite a few times. I'm seeing the memory problems combining with a kind of continuous compulsion to fall in love. The depression and anxiety may aggravate the problem.
Polyamory isn't necessarily a bad thing per se, but anything that you crave so much that it is messing up your life, is probably an addiction. If you're truly poly, you need to get the compulsion under control, so that it's a healthier state of poly.
Perhaps a place to start would be to write up a list of reasons why you love your current girlfriend. Then, post that list somewhere where you can easily see it and add to it.
At some point, you could have a talk to her to see what she could tolerate, what she'd need in order to be able to tolerate, and above all, to tell her what you really want. But you need to figure out what you really want, and right now I think you're somewhat undecided.
Feel free to either dialog with me about this on this thread, or, start a new thread on the topic in the "Poly Relationships Corner
You seem to have a tangled bunch of issues, so you'll need patience; this won't sort out over night.
Glad you're here in any case,