I'm a young ftm,

How do I explain to my ex (father of my unborn son, due date is tomorrow) that drinking heavily, smoking weed, and using narcotics/opiates (I'm not really sure what it is), isn't okay because we have a baby that's about to come? He doesn't see it as a problem since he isn't born yet. And I've told him multiple times that I don't want that around me or our baby. He just says that it doesn't matter, the baby isn't "real" because he hasn't been born. He's been out and about every night since I was about 3 months pregnant. He's only 18. He won't stop, I'm not sure what to do. He isn't addicted to it. He just does it for fun. Last night on his friends snapchat they were using pain pills. I don't want him to become addicted or for it to become a problem. I've dealt with this before as my father is an alcoholic & I had to move out because it was so bad and I was not letting my son live in that. But it was a little bit easier because my dad doesn't have to come around my son, and all of his kids are grown. Just need some advice.. I want to talk to him the right away, and let him know that it is a problem.. Because with the way he's going I don't see him stopping anytime soon. Any advice will help, no bashing please.

Edit: I do not live with him, we are just around each other a lot. I'm not around him when he is doing all of this, though.