My friend is a boy and he used to like me and I dodnt like him and now he has a girlfriend an I like him?

Okay My best friend is a boy and he used to have a crush on me he asked me out several times,gave me flowers,gave me secret admirer notes.And I told him that I really just wanted to be friends and so its been a few years now and he has a girlfriend............therefore I like him and he just wants to be friends! I have no clue what to do and his girlfriend is a good friend of mine so I have no clue what to do HELP ME!!!!!