How to confess to your best friend that you are gay and you have been in love with her?

We have been friends for 10 years. She does have a boyfriend now, but I never mind because she change boyfriend all the time. She never feels secure in a relationship because of her parents divorce. She never suspects that I am gay, because I am not a very boyish kind. I am quite famine and I always helps her with everything and I really take good care of my best friend. I wanted to confess because she never lied to me about anything and I think I shouldn't hide anything too. But I am afraid I might lose this friendship. Especially the part that I love her... I am so afraid she will freak out and think it is gross or something... how to confess anyway? I couldn't find the right timing or place... if you people experience this before please share... thank you so much...