regaining trust

so my boyfriend and i have gotten back together after being on a break for a couple of months. we were still in contact during the break and i had found out that he was lying to me about where he was (i never gave him any reason to lie to me bc we weren’t together and i was fucking other ppl too so it was pointless lying) and he had lied to me abt fucking some girl. i didn’t think much of it because we weren’t together so it wasn’t like he was cheating, but i can’t get over the lying. we had spoken a lot about us and what we could do to fix our relationship and be better but im verrrrry bad at forgetting things lol. how do i regain my trust for somebody? i’ve noticed i get uneasy when we’re apart and he doesn’t reply to me fast and before i wasn’t like that at all. and i dont wanna be like this because i believe he means well but it just stays in the back of my head that if he had lied to me before he can lie to me now regardless of whether we’re together or not. what are some good ways to start trusting somebody again?