Does smoking weed affect sperm?

My fiance has been smoking pot since he was 11. Hes 22 now. Yes that's right I said 11, his mother was a part in it, encouraging it. Disgusting if you ask me but whatever.

But back to my question, does it affect sperm? He doesn't think it does because he has 2 kids from a previous relationship when he was 16, but that doesn't mean anything. Im over here crapping on myself because I have PCO and struggling to get pregnant thinking it's all my fault, that we'll never have a happy family simply because I feel broken.

I have nothing against smoking pot, half my family does, just asking a simple question.