I'm not sure you understand the concept of human sexuality. The act of having sex with a member of the same sex does not make one homosexual. You are not homosexual unless you experience sexual urges towards members of the same sex. It could possibly be defined as a homosexual act, but the person is not homosexual unless they experience the urge to actually have sex with the same sex.
It is in fact consciously impossible to change your sexual orientation. You can't just one day say "I think I'm going to be homosexual today" and the next day change your mind. It doesn't work like that. This should be relatively easy to understand as you experience your own version of human sexuality every day. Use yourself as an example. If you believe it is possible, would you be experiencing the same urges a homosexual person would while observing the same sex? If not, it's not genuine homosexuality, you're just saying "yeah, I can change, see, right now I'm homosexual.... now I'm not.... now I am...".
Go to your local community college and take some classes on human sexuality, they will educate you of the facts and leave you with a much better understanding than I can give you on an internet forum.