I was dating this guy for several months and I found about his ex-girlfriend... He wants me back but I'm just not ready to re-open myself back to him. What can I do in this situation?

Everyone has an ex somewhere along the line. I don't see what the problem is really in dating him again. You don't have to commit, just have fun until you both find out what you want. Don't make a big deal about it.

What situation? A lot of missing info here, I think.