When is it time to end it?

This is a lng 1 but I need serious advice.I am in a serious relationship of 3yrs we hav 1 child 2gether and Iam expecting #2, we agreed we weren't going to have frnds of the opposite , due to bad experiences in the p.Nw this p june he meets a cousin of his bst frnd, he was talking w her behind my back I found out he stopped talking to her.Its nw Oct he came 2 me and confessed that he had been emailing f frnds frm the p and new on facebk, he then tld me he sent them emails letting them kno how he felt about talking to them after WE tld them it would be no more of that.BUT they are still on his frnds list and the grl frm June,is Now on his frnds list.He tld me he wnt delete them or the page.He is in school and wrks full-time.He regained access 2 his email when school started early sept.So that meant he added the grl frm June after the confrontation.I sumed it all up the best way I cld w the space given.Please snd advice.Thanks in advance!