Hes not even my BOYFRIEND!!!!! so why the JEALOUSY?

i have this guy friend that confronted his feelings about me. so i began to realize hes a nice, good lookin guy that i might want to have a special bond with. wat pissed me off was that the next day he'll flirt and mess around with all these girls right in front of me, and im the girl that he really likes. shudnt he have been more careful with what hes doing? so later on me and him began to drift apart, like he wouldnt talk to me and this was because i was close friends with this close friend and he didnt like it. when i confronted him about why hes mad at me and why hes not talkin to me, his answer was" becasue im jealous at how ure always talkin to mike(his friend) and not me, ure so clsoe to him and not me." and than he started callin mike all these names that werent very nice. I also heard and he told me dat he likes this otehr girl named Sammy alot, but why would be get jealus if he doesnt like me so much anymore? why does he leave everytime when mike talks to me and hes tehre with us? why does he get so jealous? and why is it that he can flirt and talk to any girl he wants but gets mad when i talk to his friends or other guys? wats wrong with him? mike lieks me to, and hes the same. he doesnt liek it when i talk to him. but either way, both of them texted me yesterday. HELP!