He doesn't see you as the one unfortunetly, just another girl to have sex with and it looks like you have feelings for him. You will get hurt in the longterm. I know this sounds harsh but if he really did have strong feelings for you then he would feel guilty after sleeping with just one girl but the fact he is going onto other girls too pretty much tells he that he just doesn't care. Unfortunetly we guys do make mistakes and let temptation get to us but if he really cared about the girl then we can control those temptations and never sleep with another girl. Sometimes we let those temptations get the better of us and sleep with a girl even when we love the girl we are currently with guilt and shame will take over our feelings afterwards. Hope that makes sense.