Help!

Alright so..me and the baby’s father have been on and off since we were around 14, were 20 and 21 now..I’ve always wanted to be with him but he just can’t ever settle down and is scared of being in a long term serious relationship. He’s told me he doesn’t want to be together, but he wants to be a part of the baby’s life..which is fine, I’m just having trouble adjusting. We still see each other all the time, and go out to eat and even have sex, so I’m just not sure what to do and how to set the boundaries. Any advice???