Confusing co worker relationship
HELP!
One day while bandaging a co workers cut finger I said I wondered if I was like a mom or sister to him. He replied "Neither, because I would have sex with you". I had no idea that he thought that. After that we started flirting a bit, and on his birthday I told him I would give him a kiss. I thought it would just be a somewhat benign peck on the lips, but he used his tongue. (I didn't.) Then he became cool and distant.
So I decided to keep things more professional. However, one day he whispered to me that he had a very, very erotic dream about me the night before. I did not ask any details. Over the next few weeks he mentioned this dream a few more times, but I would not bite. Obviously he wanted to share the details with me, though.
Eventually one day I came into the office feeling rather crazy, and I started flirting with him. He responded in kind and we were verbally flirting very outrageously. He grabbed my wrist, and put my hand in his crotch and he was hard. He then pulled me into a corner and we kissed each other. Over the next few days we flirted quite a bit. Then without any warning he got cool and distant with me again.
Since then it has been hot and cold. He will flirt with me verbally and physically, then become very standoffish.
I just do not understand this whole situation. We are both in long term relationships already, so it is not like we are going to start dating.
Thanks for any input!
EM