No idea what’s going on in this situation?

Hi, basically... there is a Guy I had a relationship with in work. Has said he doesn’t want to be with me exclusively because he’s in a committed relationship. We was being friends with benefits but he kept acting like my boyfriend getting me to sleep in his arms, calling me constantly etc. He would be like a light switch constantly saying he didn’t want to be friends with benefits anymore then he would come back and change his mind. He would then come back and tell me he wanted to be closer to me and it was more than friends. Then he would say again he couldn’t be with me.
I have just tried to work with him but every time I do he flirts with me, when I flirt back he will reject me. He then tells me he is attracted to me but is really trying not to be.
he asked me about who I was dating and get jealous and say he wouldn’t. He would find out if other Male colleagues was chatting to me and say I’m not being with you if your hanging out with people I’m friends with. He gets jealous that I am friendly with another guy he works closely with and the two of them will tell me two different stories, on both a professional and personal level. The guy who I’m in a friends with benefits situation with has been caught out lying a few times. He also gets annoyed if someone else I speak to in work knows something he doesn’t.
he has told me before he thought I had told his secrets to others so he decided to tell people things I had told him, to others to get me back. He won’t admit he’s done this to me. I have been told by 4 other people he was doing this.
I asked him to leave me alone and only speak to me when absolutely needed. He now ignores my messages and reply’s when he wants doesn’t get work done when he would before. He will answer my calls tells me he will call me back in 15 mins and leaves me waiting all day for important tasks. He will say he’s not trying to be awkward but he is and is doing the same thing he’s when he says he doesn’t like me or that he’s not jealous.
No idea what’s going on in this situation?
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