Hi @Linus27
As others have said, we all lose a bit of that old "fire in the belly" from time to time. Others have also suggested taking a little break from bass duties for a while.
I think that may be a useful approach. Perhaps just mention this to the rest of the band. Tell them you have other things that need your attention...
Maybe even help them find a dep player for the meantime?
I'm slightly older than you, and I'm more fired up than ever - mainly because I realise I don't have too many years of active gigging left, and mostly because I had a near 25 year break from playing - so when I came back to bass playing and to gigging, I had more lust for it than I ever did as a young 'un. Also, I have a day job that is very very different from music, and one that can be stressful - so music is my outlet.
That said, there are sometimes other band members who wind me up a bit, and I feel like moving on..... Fortunately, I'm involved with several bands and duos / trios etc - so I wouldn't have time to miss any particular one of them. I sometimes wonder how I find time to fit all the gigs, learning + rehearsals in - but I realise now, I wouldn't want to be without my music ever again. Of course, when music is our hobby, it's a different thing to it being our main income source, and that may have a part to play in the way you're feeling?
Either way, a short break may be a good thing - give you time to think, and to step back from it all. Another way, may be to join another band / duo or trio - just for "fun" and occasional jamming / noodling? Just wondering whether playing for a different reason, and playing different genres might help you feel in less of a "rut". Don't sell your gear just yet in any case.
most of all - best of luck with whatever you decide. And lastly, I'm sure you're aware that you won't be alone in feeling the way you are.