It all depends on the circumstances. If you break up with someone, one partner almost always has more feelings for the other, which leads to jealousy and hate etc. I have had a quite happy relationship for 7 months, but we just broke up few days ago becuase she had to move away to another country with her parents for university and I am moving away soon. Over the distance of 10 000km, it is not really possible to keep the relationship, although we loved each other, had lots in common and stuff. It will take maybe months for me to get over it, but then again, we have promised we will remain best friends. We might or might not see each other ever again, but I look at it as a happy although forced ending and am quiite happy that we can stay best friends. Ok thats enough of me babling around,as for you it doesnt seem that your ex boyfriends has feelings for you, I will say the most obvious but TALK TO HIM. Say that you still have feelings for him and see what he says. If he you might try getting together, but dont make the same mistake. Its ok to make a mistake, but its stupid to make the same mistake twice. The best solution to me would be that you avoid any sort of contact with him for 2-3 months or as long as it takes, start having fun, friends, parties etc. and maybe after you dont have feelings for him get together as FRIENDS. However its easy to say, but feelings are always stronger than logic, trust me I made the same mistake and it ended very bad. Ask yourself if it is worth taking the risk of possibly hating each other for the rest of the life (if you live close to each other and have common friends this SUCKS) or if you want to take the safe road and remain good friends, in that case isolation is the best thing to do, maybe tell him that you need to forget about him and have a deal that no one contacts the other for 3 months no matter what.... Hope this helped a bit.
Peace