You need to find out off Danny if he really did wake up with someone else or not -
the other guy may have said it to try and disrupt things maybe if he fancied you? If Danny doesn't believe that you and his mate didn't do anything, you need to know why he doesn't believe you..
Have a chat, and try not to get angry even if you have to rip a pillow to pieces while you're on the phone to stop yourself being mad in your voice..
Sorry to say it, but if he really did, then that would explain why he is trying to justify it to himself by pretending you and his mate did something, so he feels less guilty?
I hope that didn't sound really harsh, please don't hate me! I've been in the same situation x