Help please

Hi everyone, so this happened awhile ago and I cant stop thinking about him. I had a new boyfriend come into the picture and my friend kept asking me to hangout and why cant I have a drink with him when I can have a drink with everyone else. Everytime I got into a argument with my boyfriend and I told him about how I stuck up for myself and he would always light up. Well I added him on facebook, while I was still with my boyfriend. He had accepted then about a week later unfriended me. I don't understand why he would do that. He was my best friend and now I cant stop thinking of him. I think more of him then I do my boyfriend. Does anyone know why he did that. Thank you.