Can you go back to being straight?

At your age your hormones are going crazy, and just about anything with a pulse can seem wildly sexually exciting. It's too early to be absolutely certain what will always turn you on. There are christian churches which are far more accepting of human sexuality (of all kinds) than the one you seem to be following, so I suggest you try turning to one of those. The bible can be interpreted in many, many ways. Not even two denominations of christianity can agree on what was meant, so there is no need to pick the strictest version and try to adhere to that. Christianity is constantly evolving, and I'm sure you could find a minister or preacher to talk to who doesn't believe that God wants you to be celibate until marriage, or needs you to be straight. You didn't "change" from straight to gay or bi at 11. Before that age your feelings about girls weren't sexual in the adult sense, you liked them and admired their prettiness or whatever. Then your hormones kicked in and everything started to get you hot. If you can be turned on by women then you are perfectly capable of only having sex with women, even if there is an attraction to men, but you cannot change or become something that you are not. You are whatever you intrinsically are, but you can decide what to do about it. Dont choose to torture yourself, plenty of Christians think that they are the way God made them, and come to terms with whatever that is. Explore these expressions of faith rather than grabbing a few garbled ideas and making yourself miserable.