Stressed

Hey moms I need some advice positive or negative. I have been in a relationship for 6 years and I started getting bored and I would tell my friends man I wish I could just have some space and do me it led me to talk to other guys and send inappropriate things and when my Now ex found out he moved out and he is telling me that we will never get back together and it’s time to move on and now that he is gone I am the miserable person ever. Oh yeah a month after we broke up I found out I was pregnant and I thought this would bring us back close but sadly he still feels the same and he wants to be co parents with our 4 year old and this one coming. We been together since high school so we haven’t really got to explore. I have been doing everything to get him back but he is serious about moving on. Idk what to do because I can’t just let 6 years go down the drain I was just feeling so lonely at the time. should I just let him go and stop stressing because I feel it can affect my unborn. Yes I know this was all my fault but in the past 6 years this is the only time I have done wrong but he has done a lot more and I forgave him and now that I messed up he wants to give up and move on. Please just tell me wats I can move on or get over this depression