He doesn’t trust me anymore.

There’s this boy and we liked eachother a lot. He’s not my boyfriend (more like a boo thang). And one of his friends was talking to me and he started feeling on me because he wanted to have sex..(he is also ”supposed” to be my friend btw)I repeatedly said no to him and then started to leave. But he stopped me and said we could just talk about my “boo thang” since he was mad at me and never told me why. So me and his friend were talking wondering why he couldve been mad at me. I told him i was upset about it. So the next day, i saw my “boo thang” and he wouldnt even look at me because he told me his friend told him we were close to having sex. And we were not! I would never have sex with his friend! Now he doesnt trust or believe me no matter what i say i dont know what to do. He doesnt completely ignore me though because he still texts me. But when he texts me he’ll just say stuff like “yeah sure” like sarcasm and not believing anything. His friend even tried to do something for what he caused by telling him “she wont let me **** because she loves you”What do i do? And honestly.. when he was mad at me BEFORE his friend made moves on me, i couldnt figure out what i did wrong, so i figured he was pretending to be mad at me