Need an opinion ?

So I dated this guy awhile back and while we were together, he was on all Sort of dating apps, talking with girls, talking with them on the phone all that. So we broke up because I couldn’t handle the lies and all but now after about a year of us not being together, he says after a all that time all he wants is me and no one else but he hasn’t seen anyone for that whole time. I’m telling him I can’t trust you from all the lies he told and apps he had on his phone, I told him I think it would be best if you see other people otherwise how would I know the same shit isn’t going to happen again. He said that he can’t do that, that all he wants is me only. But honestly how can I trust that? Is it the best idea to let him date other people first before even concerning getting back together? Should I not at all ? What y’all think ?