Help!! i have a question plsz answer it for me plsz plsz plsz!!!?

ok i am 15.im a freshmen im dating a senior he is 18. he goes to my school..but on friday is his last d because the senios get to leave a week early.but anyways im friends with this guy named devonte and my boyfriend name is keith. devonte asked me if i wanted to go to the moie and keith stared at him meanly. then at lunch me tia and devonte were walking and we turned around and my boyfriend keith was following us but like in a distance you know. so me and devonte went in a clroom to talk to one of his friends.and keith comes in and says i dont want you alone with him. whats that supose to mena? also when devonte gave me a hug keith told devonte ima kill yo he was kidding about that but something was bothering him. if im with a guy he keeps an eye on me or tries to be somewhere close or something like he over protective.why is he trippin anyways he leaving friday. ieman i like him i dont like the other guy but whats up with that? any comments i need answers thank u. plz nothin rude