Lying cheat

My boyfriend and I ended things on Friday night, he then proceeded to apologise and regret everything and say he missed me, and we were on off okay again non stop until Monday morning- at which point we saw eachother at school and he asked me out again. I fell for it. He’d been saying for ages that he didn’t want it but that he still loved me and all the crap. I mugged myself off by believing it and saying it back, practically begging him to stay with me. While we were on off he sent me a message claiming it was for his mate, now, the day after, i find out it was for a girl. A girl he’s been speaking to for a while. He has full out commented on her recent insta now and my god it hurts. I hate myself because I still love him and want him. We had a massive argument over and we aren’t even friends anymore which hurts so much. He was my first love and I don’t know how I’ll ever move on, can anyone relate/give advice/be someone to talk to? X