OK I DONT UNDERSTAND WHAT GAME THIS BOY IS TRYING TO PLAY, HELPPPPP!?

So every winter i go snowboarding at this ski lodge. and this year i started hooking up with this kid. Everytime i hook up with him, he's really nice and says really cute things. but than after a while he just stops talking to me but he'll make eye contact. And than the next time he see's me he'll do the same routine over again. He sits with his ex-girlfriend but they don't really talk, and as soon as she got there he started talking to me. than when he started being all anti-social i heard her say "omg wheres nikk" (which is the kid im hooking up with) But she was also sitting with another boy. I don't understand why he hooksup with me and is really nice but than he ignores me? he does it like all the time?