Should I trust him?😪

My boyfriend of 5 years broke up 2 months ago, he is also my sons father. We’ve decided to give things a try, everything went well for 2 weeks.

I was staying with him a lot and spending more time together as a family. While we were broken up he was talking to another girl, they went out probably once and nothing else happened no sex nothing that happened mid August, she eventually ended up cutting him off and even deactivating her fb, today after church I checked his profile and seen that she had activated her fb and they still remain friends, I of course freaked out and immediately told him to delete her but he refused to do it because he says that I have to learn how to trust him, he was very upset and didn’t want to argue over her and said if he really wanted to communicate with her he would’ve already done it, we are planning to leave to a couples retreat on Nov 1st. I’m extremely confused and I just can’t trust him, he has lied to me before.

Now that we both are trying to change he tells me he would be super honest with me if he was still communicating with her, I just don’t know if it’s me being immature or what idk if I should just officially end things over fb