I need some help.

My best friend and I decided 2 weeks ago to give a relationship a go, basically we stopped pretending we were just friends.

He was fully aware that I had a relationship with his brother and said he had got over it. We slept together a week ago and now he is saying whenever we kiss or anything else he can't stop thinking about me and his brother.

Last night he said he couldn't get over it and ended the relationship. The last 2 weeks of being with him and sleeping with him has made me realise that I do love him and that my relationship with his brother was not love. He is supposed to be my best friend and we have always been comfortable telling each other everything but now he's throwing it back in my face and I feel like I've lost my best friend as well as my boyfriend.

I need to know the reason why he can't get over it and figure out if we can still be friends. I just need to understand!

Any advice would be welcome!

Thanks!