Liking my best guy friend?

ok so ive known this guy for like 3 years and i dont really have too many guy friends but hes my best guy friend. we pretty much know we like each other but our connection isnt really very strong yet. we usually just flirt a little n joke around right now. everything was going good until 2 days ago. we were in a cl n it was friday so we didnt really do much and our teacher n the cl were basically just messing around and me n him would joke and then my best friend woul;d joke with him too..my best friend!! and then she was all like looking at him n he started talking to her a lot..so now idk whats going on and im confused...im pretty sure that before he liked me he liked my best friend cuz hed stare at her alllll the time and on friday he was doing that again..so im like really confused and i dont kow what to do! cuz first of all, this is the guy i like, and second, its also my best friend he jookes with a lot. and plus, i dont know if i can trust my best friend...she says she doesnt like him and she thinks me n him would be good together..but if she took him from me itd be the 3rd time she lied to me about likeing the guy i like..and then stealing him from me..soooooo what do you think i should do?? please help and dont be rude please! thank you