I'd say, genuinely, that I'm happily married but for a few weeks have had what's been, certainly on my end, just a crush on a co-worker. He's some of the things my DH isn't and I can see that's the attraction, I don't and have never wanted to cheat or leave DH and I know it's just a shallow crush. Thing is the man concerned gets on well with me and friendly banter has spilled over into flirting with me, even though he has a girlfriend. He's told me he fancies me and there's been a couple of occasions where we could have crossed the line but I've said no, ending with yesterday (we sometimes work weekends) where we were alone and almost kissed but I got a grip and said no and made it clear I realised how inappropriate we were being and that we'd have to take a huge step back and be very clearly just colleagues. He s asking for more but in the end accepted it. I felt I'd been stupid to 'play with fire' by flirting at all but had done the right thing in the end. I felt happy to 'end' it (not that anything really went on but just to draw a line under the possible slippery slope).
Today however he reveals to everyone he asked his girlfriend to marry him that same night, ie must have gone straight home and thought 'may as well stick with this one then' after offering to leave his gf for me. AIBU to be upset that he would have been happy to run my marriage and is now trying to start his own literally hours after getting knocked back? Feel like he's taking the piss out of me and her.