Im having trouble with my bf?

There is this boy called mitch and he is bi, and my bf got tipsy and they kissed. I asked my bf if he had any feelings for mitch and he said a little bit. Then today mitch added me on msn and said to me that my bf said he loves us both equaly, and he wants me to dump my bf for him, But i wont and my bf won't dump me either. And i told my bf to tell me that he love no one else but me, He told me how much he loved me and he love's no one else. But i dont want to be stuck in some stupid love triangle. Mitch said if my bf says anything else about him and my bf then he will tell me. But should i believe that my bf said that or not? What should i do about mitch? And how can i make sure they never kiss again?