My 13 year old son and his thoughts about sex?

Talk to his dad about it. Even though you aren't together anymore i'm sure you are both mature enough to be able to talk about sex ed for your son without fighting about who is raising your son. IDK if that would be a problem but some split up parents do fight about that. I honestly don't know much about raising a child since i'm only 21 and don'y have any kids yet. but I do have friends younger than me so I know that kids these days are having sex at 13 and some girls even younger. while talking about it don't pressure him to not have sex because that make kids want to rebel and do it sooner. instead talk to him about what sex means (which may vary depending on your beliefs) how its about love between a man and a woman not just physical pleasure talk to him about what could happen try to make him really think about it having to raise a child at his age and the possibility of STDs (on this subject you can scare him with pictures off the internet) and make sure he knows how important it is to use protection. remember you can never truly keep him from doing what he wants to do kids always find a way. but you can make sure that he knows what he is doing and how to prevent the worst from happening. Good luck I know it can be hard (you should of seen my dad lol) for parents to talk to their kids about sex but it is important to do it before it is too late.