He's not necessarily sleeping with her now, but there is a very good chance it will happen again. The thing is, guys tend to look at their past lovers the same way armies do after they've planted a flag on a foreign country. That is, it's conquered ground and he can do with it what he chooses even after the initial invasion is over. There is a good chance he put a lot of effort into scoring with her in the first place and he doesn't want all of that work to go to waste. Thus he will go back and dip when he chooses.
Don't worry, it's probably not emotional, just sex. He probably just says he loves here in a friendly way.