Hi Op. I’ve been in exactly the same situation as you. Partner of 20 years, early 40s.
Crush was a supportive colleague who I only saw the best of at work. It was exciting and told me he had feelings about me which made me feel wanted and alive.
I never acted on it but the thoughts were overwhelming and consuming. I would literally be thinking of scenarios 24/7 , it was a pure chemical / physical reaction.
I ended up leaving my work , not just because of him but I wasn’t having the best time there anyway. The space between us grew and that definitely helped.
I had a few months where we would message back and forth, and all it did was stir the fire. I ended up being distracted and mentally it took me away from my partner and children.
One day my partner sadly asked me what was wrong as I seemed so different. I ended up telling him everything.
He asked me to block the colleague and to see how I feel. He’s been amazing and supportive which I did not expect and made me realise what a fool I’ve been.
In my opinion, the more you feed the thoughts about the crush, the more it takes you away from the important things, your partner, your children, your life. It’s very likely to be perimenopause, and these feelings never last. Even if you made a go of it with your crush, those feelings would subside over time.
I hardly think about the crush now, and I’m utterly appalled of how I used to think about him. At one point I was ready to risk it all - I didn’t know him at all, not really!
As humans we crave connection with others, it’s a natural thing. But don't let it rule your thoughts and distract yourself as much as possible. And try and find icks about your crush, imagine them on the toilet for example!!!