It’s definitely not impossible – you’ve already taken the first step by admitting you want to move on. You’ve already recognized all of the characteristics you don’t like about him (reasons which are totally valid, by the way!), so figure out what’s keeping you from moving forward. If you can pinpoint what’s holding you back, you’ll be able to plan the best way to stop dwelling on the past.

Are you having a hard time moving on because you two share a past together? While it’s tempting to like someone because it’s comfortable or because he already knows you, you’re still young, and you have so many more people to meet. It’s better to move on now than to keep stringing yourself along only to end up unhappy later. Do you find him good-looking? Physical attraction is important in a relationship, but trust is important too, and your guy sounds like he doesn’t deserve your trust (or his girlfriend’s). And if you’re friends with his girlfriend, you shouldn’t risk ruining that friendship for a chance at a relationship with someone you know isn’t a good guy.