My boyfriends friend told him i slept witnh someone he reli h8s?

my boyfriends friend is like a big bro to me but recently he got a bit drunk and convinced my boyfriend i had slept with someone he really hates,, i didn't and would never do that on him we are 18 and 19 i love him and we have 3 beautiful children together he has left and me and the kids haven't seen are heard from him in two days what should i do to make it better his friend has now left because he nos he done wrong lien but he is not willing to tell the truth and unless he does there is nothing i can do to make him believe me i don't wanna lose him over someones lies