Why this?

Why would a guy make it awkward for a girl when hanging out with him and his friends? And be totally against her being around him because of a past fling

Please do elaborate my dear lady.

Okay, for example, tonight after she walks in the room he greets her then acts like she isn't around and goes in and out of the room like he can't stand her. Then , the time he talks to her , he goes far away and purposely feels up another girl in front of her to make her feel jealous. And stares straight into her eyes like a "are you mad now?" "are you jealous?"

I don't understand why he's treating me like crap like i've done something wrong. All i did was sleep with him twice .