You are very much in danger of creating the situation you most fear. This man has done his best to turn his life around and yet it’s not enough for you. You accuse him and distrust him.
I’m not saying I blame you for your trust issues. But I do think you need to put this into perspective. You two started seeing each other when you were only 17. It sounds like you were more ready for an exclusive relationship than he was during your teen years. He fooled around. He even left you when you were pregnant! You had every reason to show him the door.
But then the baby came and it seems your guy woke up. Since then, he’s done his best to grow up and be the man you and your child need. To keep on course, he needs your appreciation and your confidence in him, not your accusations.
It’s very tough to give someone second chance. But in this case, the baby is the difference that seems to have made the difference.
Ultimately, trust is a gift we decide to give someone after they’ve apologized and done their best to make things right. For your own sake and your baby’s, I hope you can give him that gift. That’s your share of making this threesome into a family. His share is to continue with his decision to be a committed partner and father.
I wish you well.