Friends with benefits

gemini g says:
I had a friends with benefits situation with a guy friend who had a gf last summer. Things got complicated between us because he started to treat me badly. Ignoring calls and standing me up. He stopped speaking to me for a while. He broke up with that gf and now has a new gf he has been dating for 4 months. He hadn't spoken to me in 4 months and out of the blue last week he called and asked if he could come over. I let him.
We both talked about how we missed each other and we had sex. He spent the night cuddled with me and said all of these good things. He even told me that he wanted to be my "bf on the side". Friends told me that he was happy with his new girl so why is coming to me for sex? I felt bad about myself, especially since I haven't heard from him since he left my place that morning and I've been avoiding any group get togethers with our friends because I know he'll be there.
If he is so happy with the new gf why is coming back to me for a sexual relationship? 

You are being used by a guy who wants to have his cake and eat it. This is not going to end well whatever happens, and if you want to spare yourself some hurt end this now - and DON'T let this jerk back into your life under any circumstances.