I think you getting into recovery for yourself is WONDERFUL! I think its a good thing no matter WHAT your history to self evaluate and work on your own faults.
I think if you feel it is a fault to not want to stay with your boyfriend if he is bisexual it is your right to do so. Your opinion is valid, and is built on your own ideals of what is moral, ethical and good. I just dont agree that it makes you close minded. :-) I think that it is hard enough to go through all you are going through to then have to face this. Real or not - it brings up all sorts of insecurities related to "competition" and concern. I dont think there is anything wrong with anyone being bi-sexual, gay, straight - honestly I dont care one way or another as it doesnt affect me. When it DOES affect me is when its how my partner feels. I too would have to really think about if I would be OK with a bi-sexual partner.
Granted, my reasoning might be a little different. I dont think I would have cared about bi-seuxality previous to this relationship. I do think I would care now because I have become incredibly insecure from how my husband treats me, and that would just add another layer of that. I too am working on myself, to overcome these insecurities and trying to conquer my own faults, basically trying to take my life back!
Like Traveler says - dont beat yourself up about it - right now you are in a tough situation, and this label just might be too much to deal with and that is OK. All you can do is be honest with yourself and with your partner. If you want to change that mentality, there is nothing wrong with that either.
Hang in there!
*** rising from the ashes like a phoenix ***
Though my soul may set in darkness, it will rise in perfect light;
I have loved the stars too fondly to be fearful of the night.