Now i’m the addict

I (21F) have been in a relationship with my boyfriend (21M) for 3 years. In January of this year I found a porn site in his history. At first he denied everything and then admitted it saying it was the first time, but everyone here knows that was definitely a lie.
He had given me access to his accounts and because he uses a different browser he didn’t think everything would be saved to his Google account, but it was and that’s where I found everything. A lot, a lot of porn and he was also looking at girls on TikTok.
He begged me and told me he would go to therapy and he did, but only for like 4 or 5 sessions. Then he told me he felt like he had already healed from the issue and that his therapist was starting to focus more on our relationship.
The thing is now he swears he hasn’t watched porn anymore. I have access to everything and I haven’t found any signs that he is doing it again but I still can’t believe him.
Now everything in my head is “he’s watching porn” or “he’s looking at other women” even when I have no proof and it’s killing me. I keep looking and looking and I never find anything. At this point checking has become an addiction for me.
I’ve also started reading stories from other men who had problems with porn and most of them say they relapsed or that they couldn’t quit. So it feels weird to me that my boyfriend supposedly got over it so quickly.
I don’t know what to believe anymore. I don’t know if I should trust him or if I’m just waiting for the next time I find something.

I really need advice because this is seriously affecting me