He likes my best franid i should be mad right?

you should be mad because its not like hes still single, then he could like 2 girls at once and it should be ok, but since he is going out with you that is just wrong. if he hasnt broken up with you then you have all the right to be mad at him for liking somebody else, just make sure your best friend doesnt try anything. dont force her not to talk to your boyfriend just tell her he likes her and that you are afraid he will cheat on you or something like that