i was wondering if someone could help me...

so i'm in some serious stuff right now... im being torn between three people. two girls and a guy. im dating the guy and he and i are kinda engaged. one of the girls is pissed at me for that exact reason but has told me she loves me as i love her. the other girl and i have actually talked about marraige. the guy likes to flirt with other girls and sometimes won't even acknowledge my existence. i'm only 15 so i am completely lost. can anyone help me??? if anyone can, please send me a message. yours truly, luna.