Devastated 💔

My boyfriend and I broke up a month ago, we've been together almost 7 years and lived together almost 3.. we broke up because I found a weeks worth of constant messages between him and a female he met while out with his friends. He was upset that I was invading his privacy and claimed I didn't trust him. Everything ended in a big fight and he left. We talked a little after the breakup and he said he wanted time to himself and we'd be together again one day just not right then. We haven't spoken for three weeks and I find out he already has a girlfriend. It crushed me. He seems to treat her way better than he treated me and it makes me feel like maybe I wasn't good enough.. he told one of my close friends he didn't love me anymore and he was miserable with me. That hurt worse than finding out he had a girlfriend.. so I text him today and told him how I felt. How I didn't understand what I did wrong and this and that and he said I know I've treated you wrong and I'll have to live with that but you could've just left, and he said we should forget each other ever existed. We pretty much ended the conversation there. I've never felt so lost and hurt. I just don't know what to do.. I need advice or something.