What should I do

My boyfriend Had stopped talking to this girl Bc of their Past, and He lied to me and said “NOTHING HAPPENED” when they had stopped talking, he cried over her and he was emotionally not there But they almost dated, she told him a bunch of things like “I let guys cum inside of me” and how her nipples are pierced, she told him her bra size and everything and the day we went on a date they were flirting and he told me, that they almost dated a year ago and nothing else happened, and when he showed me his year book, she wrote stuff about how she would miss their cuddle puddles and what not, and NOT even a month ago she messaged him through a friends acc ALTHOUGH she knows how uncomfortable I am with them talking and my Bf apparently texted her this after saying he wouldn’t talk to her again, and Then he says “I understand why she’d be jealous of you” WHICH I find VERY VERY wrong 😪 I just don’t know what to do, weve been together almost ten months.. but I’m so broken, but I love him, like I don’t want to lose him but Something is screaming at me to let him go I don’t even know how to talk to him about it anymore