Yep, OP. It is wanting the closeness with the other person, in every sense, wanting the barriers between you to break down. Obviously very unwelcome feeling if you are married.
It happens to everyone, man or woman, unless you have been married 5 mins and are still enveloped in each other. Every LTR would have had several crushes on his part or her part. It is what you do with these feelings that matters.
If I get a crush, I work on keeping the distance and NOT getting closer to the object of my crush. Best policy is wait it out, do nothing. It’s not the first, it won’t be the last. Unless you want to change your partner every two years when things settle, you have to learn to walk away and give up these ‘opportunities’. I also note I tend to appreciate my partner more after such an episode. Sort of a reminder why I married him and not anybody else.
I also think people are not made to be monogamous. We are built to look at others, to like newness rather than same old, to be excited by discovery, not to get the kicks out of the routine of 20 years. It is hard. But it is the fear of losing your partner that stops any funny business. Not because you go brain dead after marriage.
I always think it is strange how nobody bats an eyelid when you say you have got several good friends at once, but you cannot say that about romantic relationships. It’s supposed to be one and only. Well, it’s not natural really. One can connect with several romantic partners just the same as we connect with different friends, I can imagine this perfectly well. You don’t say, oh you can’t have another friend, you have got one already. Or one friend at a time. Sounds ridiculous, doesn’t it? I see it as being the same. It is a connection to the other person, you can have this connection with several people, love them in their different way, have the closeness special to them. Just as you do with your different friends. But we don’t with romantic partners, because it’s not socially acceptable and our partner would find it hard to cope with. As we don’t want to lose our good long-term partner, we don’t explore those avenues.
So don’t sweat, it’s commonplace.