Why would he say this when I'm dating his best friend?

i tihnk you should tell your boyfriend. after all he is your boyfriend, and if that was happening to him with one of your friends you would want to know right? i say you tell your boyfriend and let him know how uncomfortable this is making you. that way he will either tell his friend to back off or keep a closer eye on him. dont feel guilty,,, you did NOTHING wrong! good luck hope i helped