Because they are just plain wierd i mean i never would do that to a girl.
Me being a guy I know- it means he likes you and can't take aeein you talk to other guys if you like him get to know him more
in my oppinion its probly because he is used to getting all of your attention not liking the idea of having to share it with what some guys may view as competition!
Because he is possesive,dominating, and insecure. He needs help, You RUN.
Erm im going to answer this question with another one. Why would you pretend to be jealous? If you really like this girl, im assuming its a girl i could be wrong, you wouldn't need to pretend to be jealous. And you don't need to show off, she'll like you for you not who you pretend to be.
He probably likes you back.
He probably likes you too
because he likes you to! :D
It means he's really into you and wants to see if you like him back!!!
cuz hes into you, moron.
maybe he really likes you and doesn't want you to be with nobody else but him because he really cares and love you so much and want to be with you
simply because he they still like you and are jealous of who your with now simply because they like you still and are jealous of who your with now
they would get really jealous and they would want you more. its like playing hard to get. if they like you, they would get really protective and want to be better than that other guy.