You have to make up your mind that you aren't going to let the past relationship with him affect you. If its over, then be happy about it and move on knowing that you are a better person after having met him. Breaking up may be hard to do but you have to ask yourself if you would rather be happy that there are other fish in the sea or if you would rather be miserable asking yourself "what if" every time you see him. And if you cant make that decision then the easy answer is MOVE. If you aren't stuck in a lease, you really ought to be looking for somewhere else to live. And if you are stuck in a lease ask your rental management what it would cost for you to break the lease. You may not find a place as nice for what you are paying but thats the price of dating your neighbors. Another option would be to just modify your schedule.. If you find that the times you come and go cause you to run into him, then start leaving an hour earlier or an hour later depending on what your schedule would permit. And if all else fails, find you a "safe guy" who might be a platonic male friend who really wants to get intimate with you but does not have the guts to make his move. He will be so glad just to be in your presence that making him sleep on the sofa will be acceptable to him. That way you can make it appear to your ex that you have moved on to bigger and better things without getting emotionally involved with this "new" guy.

The 'safe guy' idea is very cold blooded. You totally disregard this guys feelings. He will most likely wind up getting hurt just to fulfill your agenda. I guess it's difficult to empathize with men, huh?