OP, I have not been married as long as you have, but I’m familiar with the feelings you’re having. I wonder about counseling for yourself, possibly for depression. I mention that because I’ve most commonly (though not exclusively) experienced these feelings when I suffered from postpartum depression.
I think, honestly, that my husband means well, but when we get into this kind of rut I feel like he sees me as a machine and not a person. He greases the squeaky wheel, so what am I sad about? And then he sees expressions of need as accusations of failure on his part, which makes him defensive, so then we argue about whether or not it’s reasonable for me to have the feeling, which is pretty silly because emotions aren’t reasonable.
To some extent, I think this might be a male and female thing, because most of my close female friends have experienced similar treatment. We’re married to very good men, but it seems like our husbands want to just check off a bunch of boxes. If we deviate from the expected happiness level, we can’t expect them to change or try anything new, because they’ve already done the protocol, and don’t all the marriage books say women just want men to listen, not do anything? (I get that one a lot.

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(Of course, what’s tricky is that women are changing, all the time, to an extent that men don’t. Or when entering perimenopause or menopause. This is probably a big part of why men find women so unfathomable.

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I think it’s worth seeing what you can do on your own, but also it might be worth it to express to your husband, “I feel really disconnected and like we’re just going through the motions. Can we try something different? The old stuff isn’t helping, even though I know it used to.”