Hi prettyeyes
Firstly, I wanted to say I'm really sorry for the circumstances that you've gone through in your life. You've gone through a lot, too much to handle on your own. I hope that you are seeing a therapist to help you deal and process these emotions.
I think that the anxiety could definitely be related to past experiences. Your experiences are significant enough to contribute now to your overall well being, which is why you need careful support to help you manage this. You deserve to get better.
I think research is exploring a number of facets of bipolar, from environmental to genetics etc. I'm not sure there's one specific answer but maybe someone can help us with this one.
I thank you for sharing a bit more about yourself and I look forward to seeing you around on the forum more often. You seem like a really nice person.
Take care of yourself. We're here to support you.