You are not retarded, and he is not facing the abuse. It normally takes a while before the survivors connect the dots between the abuse and the behavior.
It is tough, he needs to understand what has happened, and be willing to go for help, It must be his decision.
If he does go for help, then it must be a therapist that specializes in CSA.
Let him read the material on a site called AMSOSA
the info here is written in plain english and is easy to understand. He might be able to connect the dots here.
Just support and love him but DO NOT ENABLE him. DO NOT condone his bad behavior, and don't allow him to get away with viewing porn or chatting to people online. Just because he has suffered abuse does not mean he can miss-behave and treat you badly.
Go to the site with him and read through a cuple of the pages with him, ask him if he feels like this or does that sound true, and if these behaviours sound like what he is experiencing. DON'T FORCE HIM. Do it in love, and I am sure that all will start to mend.
Feel free to ask questions anytime, or to PM me anytime.