I fell into a situation like this. He had a long distance online girlfriend and in retrospect I think he was using me as a substitute whilst they were apart. We started off as friends then became inseparable and I, stupidly, fell in love. I never told him and I think both of us felt as long as we never kissed or engaged in any sexual activity that it was ok and we weren’t hurting anyone. Not true. I was left devastated (6 years on, I’m still not over it) and although his now fiancée doesn’t know I even exist I’m sure she’d be really hurt too if she ever found out. Like you he initiated a lot of the inappropriate stuff, was constantly texting, snap chatting etc, was very touch feely, made it clear he wanted to spend time just the two of us away from work (and towards the end we did, several times a week), wanted to stay up talking just the two of us till the early hours etc.
At that time, one of my closest friends advised me to send her an email as if I was writing to him, getting everything off my chest. She read it and said I needed to send it to him but I never did. I found it the other day when I was changing phones and transferring emails.
My biggest regret is that I didn’t send it. I really should have. It explained my feelings about the mixed messages, how difficult it was at work and how I thought he would behave differently if his girlfriend were there and that I needed him to back off. I said that I wanted to be respectful of his relationship and that his behaviour was difficult to cope with. At the same time, I explained that I didn’t want things to be awkward for us or our colleagues and that I didn’t want an atmosphere. I laid out the behaviour that needed to stop I.e no physical contact (hugs etc), no time alone or social time outside of work, no texting unless it’s strictly work related, he’d have to arrange travel (I drove him to and from work) etc.
Anyway, it seemed really sensible and as I say, I really should have sent it. I understand how an emotional affair can creep up on you. I saw the signs emerging with another colleague recently and now I am aware of what can happen I’ve managed to shut it right down in the early stages. It’s not easy but it’s doable.
I think it sounds like he was initially attracted to you and that you sort of rebuffed him due to your circumstances? The man I mentioned used to get so angry and upset when he thought I was dating (even though he had a girlfriend!). It’s possible that the whole girlfriend situation was an attempt to either make you jealous or move on from you. There seems to be some attraction on his part. Either that or he just enjoys the game playing. Bottom line is, if it’s affecting you at work it’s really not ok and you need to make that clear.