The best thing you can do is be yourself. Your whole self.

Maybe try telling yourself & also believing, (because it is the absolute truth), that a person is with you because they want to be. Trust me on this, if he didn't want to be there, he wouldn't be.
And ~ it is unfair of you to put the 'sins' of another onto him. He has not proved to be untrustworthy, so don't make him carry that weight. He is a different person.

Then relax in the knowledge that he is with you by choice. Don't try to read too much into things.
Do your best to be yourself, not only your best self, but your real self & encourage him to do the same. Agree on absolute honesty about intentions & feelings. Transparency is key and it is how you really get to know someone. And learn to trust.

I wish you only the very best as you move forward...