Or possibly being massively naive tbh. As I was only 9 or 10 when I heard about it in the playground and that was the late 80's!!
Anyway he asked me where babies come from on the way to school this morning and I started to explain to him in basic terms (whilst CRINGING) and I just got the feeling he already knew so I asked him and he said yes he knew 
Just feel sad I suppose that another part of his innocence has gone. He already doesn't play with toys anymore, it's all about his Xbox, wwe wrestling, mine craft and his phone. (Btw the phone only has games on it, he can't call / text / go online)
Also I am shit at explaining things and I don't know if I've explained it very well to him
and the last thing I want is to confuse him or make him feel like there's something embarrassing / wrong about sex...as my dm was awful at telling us about sex and somehow made me think it was embarrassing, wrong and shameful. and tbh it had the opposite effect as I went out and did it at 13 and slept with absolutely loads of boys (and men) before I was even 18. And tbh I still now have issues around love / relationships etc
I just want my dc to feel "normal" about it, and understand it properly, so any advice would be very handy right now. And any suggestions of an age appropriate book we could get him maybe?