Mixed signals

Myself & a coworker have been flirting heavily. He initiated everything. We both are already in relationships but the flirting is fun. He acts like he's into me but at times he is hot & cold. We have talked about being physical but haven't been as of yet. Some days he says things to make me jealous & laughs about it. Bragging about how he would be out of control if he worked in a different dept where there are more women. He even told me he wants a friend of mine to oral him to get back at her man by spreading it around the job. I dont believe him cuz he is private. & at times if i ignore him he'll go out of his way to regain my attention. He is 13 yrs my senior & i have other male friends that occasionally talk to me. He sees & says to me i have too many men in my face & 1 time i was on my phone, he said who u talkin to, your boyfriend? I was on facebook. Was that a sign of jealousy or possessiveness? He has even come so close to my face to kiss me but won't. I don't get it. Can anybody tell me what is the deal with this guy?