This has happened to me fully once and almost happened for a second time recently and I realised and shut it down immediately.
The first one was very difficult as he was a work colleague in a very long distance (Australia) relationship. We enjoyed each others company and always chose to work together as we seemed to make a good team, then we started taking our breaks together, then progressed to lunch every day just the two of us out of the work environment, then lunch and dinner just the two of us etc. It sounds ridiculous but it snuck up on us. We hung out a lot just the two of us outside of work. He’d always ask me to be his plus one. As well as seeing each other at work everyday, hanging out together, we’d snapchat and Facebook message each other a lot. That progressed to him being very physically affectionate with me, everything except kissing and sex. I was in love. It was fucking awful.
The only way I got over him was to cut contact completely. I blocked him on everything. Moved job. Moved home. Extreme, I know, but the whole situation was torturous and had went on for a couple of years.
I now feel extremely guilty about what I did, being the other party in an emotional affair and being in love, to his girlfriend/now wife although I’m sure she has no idea I ever existed.
As I say, it almost happened again. This time I shut it down totally and almost immediately. There was a difficult couple of weeks but I just put all the angst into trying to meet someone who, like me, was single and available and made me feel all of the positive things these men did without any of the negative shit. The second guy, I will have to see regularly as he’s part of my friendship group and almost like family but I don't encourage any of his attention, don’t connect much on social media, make sure never to spend one to one time with him, when he does have to message me I don’t get caught up in chit chat or conversation that could lead to anything more. I know what to watch out for this time round and what leads to the awful limerence state.
In a way, you are in a more fortunate situation (although much more risky) than me. On both occasions I was single and very lonely. I know you can be lonely in a marriage too but if it was me I’d use this time to invest more in my marriage. What’s lacking from it that you get from this other guy? How can you rekindle things a bit?
I get that the initial part, of breaking contact, feels unthinkable. You’ve got this person in your life who you love connecting with, who makes you feel amazing, who you can’t imagine ever not being in your life and who makes you feel so happy. How can you live without them?
But you can. It gets easier. I promise. The idea that many years down the line I could have still been stuck in that situation feels like it would have been hell. I do still miss him (the first guy) a lot but I can and am living without him!
No contact is the only way. Trust me.