How do you rebuild trust after cheating?

My boyfriend cheated but we are trying to work through it (I think). I still don't trust him and now he does not trust me because he knows he was unfaithful. He has been in contact with other girls since because he believes now I am unfaithful to him. Anyway how can we work through this? Being asked everyday if I'm cheating & who I'm texting is exhausting. I care for him and want to be with him since we are having a child, but I don't trust him and it's really annoying being constantly asked if I'm cheating. It makes me want to break up with him!! How can we fix this?

Also he has been in jail now for a couple weeks. So every time he calls me from jail he is asking me who I have been hanging out with. The way he asks is so pressing and accusatory not to mention annoying.