One thing you should remember is that all the feelings of fear, shame, confusion and guilt that a boy picks up during abuse will continue with him over the years. They may sink below the surface where they are difficult to identify, but man, they are still there! I remember from my own youth that by the age of 14 I had learned that sex is only this: something that adults do to children to hurt them.
It doesn't surprise me at all that you have been affected like this, but the point is that there is nothing wrong with you. What is fucked up is what was done to you by the babysitter.
Your therapist will help you to see that the way forward isn't to aim directly at the problems with erection, orgasm, intercourse, and so on, but rather to focus on why you have these bad feelings in the first place. That may take some time, but just believe in yourself. You can do this!
Keep posting if you can. It is always better to talk about things and let your feelings out, rather than bottle them up.
Nobody living can ever stop me
As I go walking my freedom highway.
Nobody living can make me turn back:
This land was made for you and me. (Woody Guthrie)