Lose the new chick and go back to your ex.

This girl is going to keep stringing you along. What's preventing her from staying with her bf AND hanging out with you if she can manage it? She obviously will cheat on her bf with no problem (since she already has), and she knows she can go to you and get what she wants too. She's messing with your head and you're going to end up hurt in the end. And since your ex is your **** buddy, then she's totally still into you because she wouldn't subject herself to that if she didn't want to be with you.

And you, if you DO love your 8month girlfriend, then stop being a prick and go back to her--otherwise you're going to lose something really great because of a temporary lust that is just messing with your head and taking whatever she can get.

__________________
Cinderella said to Snow White
"How does love get so off course
All I wanted was a white knight
With a good heart, soft touch, fast horse
Ride me off into the sunset
Baby I'm forever yours"