Tbh, I think the best way to approach it is a lot of self talk.
You were alright before you and you'll be alright after him.
If he is a cheater, and wants to cheat, he will, if he isn't, and doesn't, he won't. It really is as simple as that. And you have no way of knowing which of those he is until he either cheats or doesn't cheat.
And you will never know.
He might never cheat. He might cheat 5, 10, 15, 20 years down the line.
He might cheat and you'll never discover it.
I know this probably feels.Like I'm sticking the knife in but what I'm trying to say is that if someone hasn't given you reason to doubt them, you just have to get on with it and choose to trust them until and unless they do give you a reason.
I've been cheated on and treated badly in relationships but, if do date someone, I keep my eyes open and my worst about me but I always trust them until they give me reason not to (which they always do, but that's another story...)