My Best Friend and I Had Sex, But Now He Won't Date Me

A couple of years ago, I moved across the country to work with my best friend. He and I have known each other and worked together for almost 10 years. In that time, we have become exceptionally close. He always had a girlfriend during that time (she made him absolutely miserable, but he wouldn’t see it). Since my moving here, she has cheated on him and then left him. He took it really hard, and I have been trying to support him through it. Recently, we were drinking together and had sex. Then repeated that several times over the next few weeks. I never asked for anything more, but then all of a sudden he started saying that he would never date me, over and over again. I am so hurt and don’t understand this sudden change, except that he likes younger girls that are prettier than I am. I’m trying to recover my relationship with my best friend, but it’s hard in the midst of my already diagnosed depression, living across the country from all close family, as well as dealing with my father dying last year (and I was his favorite, we were very close, and my best friend was also close to him).