Most Helpful Girl
If you want to be friends, don't sleep with him. You're basically showing him that it's OK to leave and date other women because you'll be waiting to take him back when it's convenient for him. He's not into you, and he went through the motions to get laid. Too many people these days will use the label of BF/GF so that they can sex without feeling bad for it. Or he doesn't know what he wants and is not willing to commit and left you because he felt trapped. Maybe he's not over a serious ex and he's serial dating to try and replace her. Either way, this guy has issues, and you won't get anything real from him.