My son was molested. Im worried

My son is 19, male, and has special needs. He is non verbal, he can't walk well, and has a low IQ.

My ex-wife and I no longer live together and I just found out that one of my her friends who used to watch when he was 14 used to sexually abuse him. And he never said anything. Not until now... because apparently it just happened again... when he went to visit his mother. He's begged me not to tell anyone. And so far the only person I have told is his GP.

I am very worried about him. Sometimes when he get really upset he hurts himself. Sometimes on purpose other times its just because his ticks get so bad, he can't control himself. He has been laying in bed all day.

Added: My sons GP knows he had sex. But he does not know he was raped. Which is why there was no mandatory reporting.