Is my boyfriend gay?

I have a question about my boyfriend and I want to know if what he is doing is normal. I am aware that he enjoys watching males masturbating and it turns him on. We are together for almost 4 yrs now (1yr LDR) and even when I say that I am okay with it, I am still uncomfortable about it. Is he gay? Am I the one who have a problem? He is my firsy bf and I am his first gf. Just to add, there were times that even when I am available, I catch him doing it in the bathroom with images of guys jerking off. I do love him and I don't know if I can fully accept him as he is. The only thing I am considering about his situation is that he said, he was molested when he was around 5 to/or 8 yrs old by a guy neighbor. He said that might be the reason why he cant stop it. I hope you can help me uderstand this. :(