Cheater or no??

so basically when me and my bf were just thinging, we met up for the first time on Valentine’s Day and cuddled and just talked. Then we couldn’t see eachother for a while and we were not dating at the time, but flirting and thinging, I had cut off all guys for him at that point. Even after we met up he was like “I wouldn’t have wanted to spend Valentine’s Day with anyone else.” Then he ghosted me for a day, he told me he doesn’t want to date anyone if he can’t see them. Then after a day, he texted me and he was crying and apologizing for letting me go and we started talking again. Fast forward 8 months later, we’ve been dating for 7 months and he finally tells me that after we had met up for the first time and AFTER he cried over me, he had sex with another girl. After he ghosted me the first time he didn’t ghost me again, meaning he had sex with another girl while we were talking. It wasn’t just casual talking, we really liked eachother. I was so hurt when he told me, even though they had sex when we weren’t dating. He told me it meant nothing and it was like masturbating and he regrets it. were thinging a lot though. There’s been a lot of other times when we were actually dating he has acted sus. For example just 2 weeks or so into our relationship he got a dating app back and talked to other girls, but when he told me he cried again and apologized and said he’ll prove to me he would never do it again. Then there were other times he was like “im losing feelings” and things like that but then we’d always resolve it. Things like this hasn’t happened recently but even though he promised me things like that would never happen again and that I’m the love of his life and his soulmate I kinda have trust issues now and idk what to believe, because honestly he had crazy mood swings, one momen he loves me so much then somehow he doesn’t care as much. He’s different now but were teens and he made a promise to me but idk II should trust him 100%? I’m just scared it’ll happen again and this is our first serious relationship, advice is appreciated ty if u read this far😅