Hmm...I think there are a bunch of good posts up top and unfortunately have no time to respond.
I will say this however...I can certainly relate. I hate labels, and don't know where to label myself. In the end, I think I have found that maybe, just maybe it doesn't matter what my sexuality is at this point and HOW it is that I have come to be "bi"--if indeed I am. At least for time being, I mean it truly does not matter...the point is, how am I going to deal with it now? How am I going to live the rest of my life?
At the age of 23, I must admit...I am more confused than ever by my sexuality. I had for the first time actually tried doing things with guys these past few months and found it to my liking as well. However, one thing I've realized is I have to be mature about this. In my hetero side, I am more of a prude--very high standards, very conservative. With guys, I still have high standards but not quite as conservative.
In the past few months, I have found myself experimenting much like a teenager would that had just found his sexual side. The key thing, however, is that I have also found myself regretting the risks I'm taking as it could potentially devastate my entire life--all the things I love and have worked hard for--from work, to family relationships, to friendships. My lust for guys lurking and waiting to express itself in cheap, one-night stands.
This I have found is due to my keeping it all in. By being in the closet with my homosexuality, I find that it is hard for me to grow in that side. I suppress it so much that when it comes out, it REALLY comes out. Does this mean that I am going to come out as "bi"? No, I don't know yet. Nevertheless, I know this...both my homosexual and heterosexual side has to be reconciled and dealt with maturely.
Okay this is getting long...the point is this (and please remember that this is just MY opinion here). I know you are confused about your sexuality--hey, who isn't? Ask yourself though if it TRULY matters whether you know how your homosexuality began? You can spend years upon years sorting this with a psychologist/psychiatrist and even they would never be 100% sure. Most scientists agree that we are 50% genetically-affected and 50% environment-affected creatures.
Do not misunderstand...if you were doing "strange" behavior like tendency for violent gay behavior, then by all means work with a psychologist and the like. Indeed, if you are used to associating homosexual behavior with the behavior that happened with your abuse, please sort that out and separate it (whether with the help of psychologists or mature, committed bisexuals/homosexuals who can help remove the misconceptions of being purely carnal beings).
However, the question of homo/bisexuality is not quite as serious (I don't think) and is something that is left for you and your conscience than anyone else. Most importantly, whatever you decide in terms of what your sexuality is and how you had "gotten it"...make sure you handle it maturely. The road will be tough for us survivors to sort through these issues. There are perhaps some questions we may never answer. Still, having been survivors, I know that we all know something about living the life we want to live. Focus on that...what you DO know to be right goals for your future. In the end, you may have found the answers to your questions simply by living the life for which you had aimed