He is messing with my head and this hurts?

[K]

Please do not bother lecturing me on this subject. I'm already hurting enough right now as it is. As most of you know, I got feelings for a married co-worker almost 2 years ago. I didn't know he was married until I was pretty infatuated. Trust me, I've tried hard to not have any feelings for him, but he leads me on. He's been ridiculously flirty with me since he realized I have feelings for him. After I quit in July for unrelated reasons, I began visiting because it's a movie theater/restaurant type place and the only one in the area. His flirtations got more intense after I quit. He's always hugging on me lately (long, tight hugs), saying sexy things in my ear, referring to himself as my "boyfriend" and jokingly asked if I was cheating on him, etc. For some stupid reason, I was under the impression we were friends. 2 months ago, I messaged him on FB and asked if it was okay if he added me. He read it and didn't reply. He claimed he never got the message. He told me to re-send it and he would add me.

I re-sent the message and he read it and again, didn't reply or add me. He admitted to getting the message, but when asked why he wouldn't add me, he got nervous and kept changing the subject and walking away. I let it go for a little while because I didn't want to annoy him. Last Thursday night, I visited and we spent a few min. talking and he gave me 2 really good hugs. I friend requested him later that night. (cont.)
He didn't accept it or deny it right away. I messaged him Friday night and jokingly asked why he hates me so much that he won't add me. He read it, didn't reply. The next night, he marked the message as unread and denied my friend request. I wasn't totally upset, but kind of. This is where I get really upset. I viewed my friend Cassidy's FB today (she still works there) and they're friends on Facebook now!!! Why will he add HER, but not me? I ONLY want to be friends with him.
I know I have deep, deep feelings for him, but I've always figured if I can't have him, I don't mind being just friends with him. It's better than nothing at all. Unfortunately, he won't let me be friends with him, at least via Facebook and I don't know why.