Do you think its right if I do it?

This is two different thing.
He cheated on you, broke your heart. Can you trust him again? You think he will not cheat again? I mean once a guy cheat on their girlfriend it's usually mean they found the other girls more attractive then their own girlfriend. (Not saying all guys)

There's this guy will sleep with you from out a town, you brought this up meaning you have some kind of sexual feelings with that guy. In my opinion you basically have the same feeling as your boyfriend did when he decided to cheat on you. Ask yourself do you want to sleep with a guy who just want sex and nothing more, if the answer is yes then the relationship between you and your boyfriend will not work out since you both start to have sexual feelings with other people.

Why would you want to be with a guy that just wanna sleep with you.

Keep both as friends. Let time tell the truth

Take care

If that guy slept with someone else he doesn't deserve you. Just break it up before you get hurt again