If you've decided to break up with him, then continuing to sleep together is only going to confuse and complicate things more. I'm not sure why you both broke up, but if you've determined he's not the right person, or not treating you well, why does he get the same benefits as someone who is right for you or who is treating you well? If you don't break this off, one or both of you will end up getting hurt. Eventually one of you will find someone else, and the other is going to be left in the lurch to suddenly have to deal with all the feelings you're trying to avoid by sleeping together. You're also closing yourself off from the opportunity of finding someone else as long as you have lingering feelings for him. If you really need to talk, you should just talk on the phone. Or only agree to meet up in a public place and try to avoid spending time alone with him.
Hope this helps! Good luck!