forgiving my liar boyfriend

so my boyfriend and i had acouple of months where we weren’t together but we were still in contact. we both were talking to other people and we recently got back together but i found out that he was still in contact with the girls he was flirting with his reasoning being that he wasn’t sure if we were actually back together and that he felt like i was still talking to the guys too even though i wasn’t. he even went as far as going on a date with a girl and lying to me about it. i forgave (?) him and i told him his reasoning is stupid and i’m pretty sure there’s more to the story than just that but i’m down to try and regain my trust for him because in a way we didn’t really act official until after he stopped talking to the girls. which i’m assuming was his fault. but idk how should i go about letting this go? because i mean some moments i think about it too much (like rn) and i get mad and i just wanna break up with him and literally never give him the time of day but when i’m clear headed i want to give him a chance and actually see his improvement. and i mean i guess there is actual improvement he does seem serious about me again but in my head i’m like IS HE GONNA PULL THAT STUPID SHIT AGAIN OR WHAT??!! i guess it’s only a matter of time but ughhhhh i get these intrusive thoughts and like if i bring it up to him like literally nothing he says makes it any better bc i wouldn’t trust a word he says. how do i get over this :-( he’s lied to me so many times and rn i feel like maybe he’s actually gonna treat me the way he used to before this all happened or maybe even better because things seem different but even then i feel like this is all a lie and i’m being lied to. or that maybe he’s just gotten better at hiding things.

and yes i am a scorpio.