Can a man change ?

I've been on and off with my ex and everything we break up it's because he's cheating I'm getting to the pint where I think he won't change I believe in second chance but at this point I just want to move on but idk how I've been trying to stay away but I miss him I'm not ready to see him with someone else. But I can't keep letting him hurt me. I need to know how to stay away .