Welcome, 46andTwo.
Another bass player here; a bit of drums (not for a long time, though), and a very, very, little bit of keyboards.
That's a really interesting question. I do recognise what you mean; I can have moments where I'm really overwhelmed and just kind of hoping that my fingers are doing the right thing, and others where I get so into what I'm doing that I drift off and then realise that I have no idea where I am in the song. I've often nearly fallen off the stage at the end of a gig because I'm so burned out (I didn't get stage fright, I got back-stage fright - leave me alone now, I don't care how much you loved my music!)
First, try to get some honest feedback from your bandmates if you can. Do they actually notice you struggling at all? My little lapses were often barely noticed by anyone else; in my head it was confusing and my attention seemed all over the place, but actually my fingers were usually doing a pretty good job without me. I was making myself anxious over nothing, and the anxiety was feeding back into my attention problems.
Think about how you arrange yourselves in the room, and whatever monitoring you have, to make sure you really are hearing exactly what you need to hear from the other musicians. The top end of distorted guitars was especially bad for me, and I didn't really need to hear it that well to follow a song, so we'd arrange our amps accordingly. There's no law that says the drum-kit has to be bang in the middle of the stage, so just do whatever works for you and the rest of the band. Use hearing protection! Work out hand signals and nods so that you don't have to shout at each other if necessary.
Band mates mucking about is a bit trickier, that's a social rather than musical thing. You can only compromise amongst yourselves how disciplined you want to be, or need to be to make your music work. Some bands work easily this way and some don't; the best friends in the world can fall out over band discipline or musical differences. If you can get to play casually with other people, do. It will broaden your musical experience, and might also find you other musicians that you're more compatible with. There's no shame in that. If it's really not working out don't try to stay together just for the sake of being a band, accept it rather than ruining your friendships.
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When you are fighting an invisible monster, first throw a bucket of paint over it.