Trust issues 😔

Hi! I’d like to start off with saying that I know I sound crazy but I need some advice. Ok so me and my boyfriend have been together for a year. We have a little boy due at anytime. Well anyways a month or two ago I found that he had been texting his ex. Nothing flirty or anything like that but I still have told him I don’t like him talking to her. Especially because she tried to get him to come over to her house when me and him first got together. Anyways ever since then I just can’t trust him. Well I don’t know if it’s trust because like I don’t think he would ever cheat on me but a little voice in the back of my head won’t stop telling me something is going on. I’ve went through his phone w/o him knowing ( I know it’s kinda crossing the line) and found nothing. I didn’t think I would I just wanted some peace of mind about it. By anyways I’ve tried to get over it but I just can’t shake that feeling. What should I do?

//Side note//

I have been cheated on in the majority of my relationships and I really truly love this guy. It feels too good to be true.