Hey, first off I'm sorry that your father and foster brother put you through that. I'll admit I'm a guy and having the total lack of respect towards a woman to do that kind of stuff to her makes me sick. I don't think anything I or anyone else can say will ever be able to really help you overcome such a terrible event like that and I'm really really sorry that it happened.
I'll be honest and say that I really don't know your (ex)boyfriend like you do, but I personally think that any guy who dumps a girl just because she won't have sex with him isn't quite right in the head to begin with. I just think that if a guy ends (or starts) a relationship on the basis of sex (or lack thereof) then there might be bigger problems to deal with than that of sex.
I know it's probably hard but I promise that it will get better, it might not be right away, and it might even get worse before it gets better, but it WILL get better. Trust me. Are you a Christian? If so there's nothing too small to share with the Lord, I know I tell him quite a bit.
Anyways, I sincerely hope things get better for you. If you want/need to PM me or anything I'll be more than happy to try and help any way I can.
God Bless and be strong.