misunderstanding

Angel
My boyfriend thinks that I like my bestfriend's brother when I REALLY DONT. He saw my friend introducimg her brother to me. I just bowed my head and gave him a little smile. And thats it. So i think there's nothing wrong with what I did. I kept telling him that what hes thingking is wromg but it doesn't work. (Btw i have cheated before and I think thats the reason why hes like this but trust me, IM WORKING ON IT we actually are doing great not until this happened) pls help me what should i say or do. I just love him and i dont wanna loose him :(