How do you deal with trust issues in new relationships?

I have severe trust issues because of what has happened to me in the past. I’m with a new guy and he’s said he’ll always be honest with me. But he started acting distant, said he just had family things come up and he’s dealing with stress from work and school. I get it so I’m trying to give him the benefit of the doubt. But I gut feeling will always tell me there’s someone else 😞 I overthink to the point where I can’t eat or sleep.