First love

I like this guy. We’ve been dating for a year and a couple of months. I love him so much, but he cheated on me two times. The first time I forgave him. The second time, I was willing to forgive him, but I can’t. He was my first everything, so it’s hard. He picked the other girl over me, and they were talking for a week while we had been dating for a year. I feel like he likes attention. He lied to me a lot, and I just want to move on, but I can’t. I’m really close to his family. I’m best friends with his older sister. He wants to be friends, but how do I tell him I’m not ready? Every time I say I forgive you, just try for me, he says “I don’t know” or “I don’t know what to say.” He says he doesn’t know how to explain his feelings. I understand, and for a year I tried to help him explain, and he was doing good. Now, out of nowhere, he says he doesn’t know how to anymore.