That sounds real horrible, and I can only imagine the pain you're feeling.
I don't think that this alone will and should define you. After all, you're an awesome person, and you have a lot of talents and abilities that shape you.
I can't say that it'll get easier, but I can say that you're in the right direction knowing what the problem is. Knowing is half the battle, and it puts you at a better edge on trying to solve it, if not handling it.
I do think you should contact your friends. Not to vent or to apologize, per se. Rather, it would have to be a formal conversation between all of you about what you're going through. Sometimes, you have to be upfront with people and tell them "this is what's happening, and I don't entirely have control over it". Moreover, because you're a bit younger, having someone that you trust there to help guide the conversation can definitely help fill in details you'd rather have someone else explain. It doesn't even have to be an adult or family, necessarily.
It'll be better to talk things out a bit, step by step, so that they understand your condition a bit more, and so that you understand their perspectives and feelings a bit more as well. And if you still cannot reach your friends or they have stopped talking to you, you still shouldn't feel like you have to go at it alone.
I'm definitely here for you whenever you need someone to talk to, and there are plenty of others here as well.