I think I've experienced something very similar. Maybe not 100% exactly the same because even each different spell of it varies in ways for me. :P
It does sound like depersonalization and/or derealization. Sometimes it feels like more than that for me, but I don't know, I guess dissociation can be complex. I've been going through a spell of it that has kinda in some ways been getting better, but definitely still there. A weird thing that's stuck out about this time is just how confused I feel at everything. It sounds weird, but it's like my brain is having trouble making sense of the world and everything, and I'm overthinking the simplest little things. The way I've found myself describing it to people a few times the past couple months is that my mood is just, "confused." I'm not confused about something particular, I just feel confusion a lot, generally. And I feel some of the thing you were talking about where it's like... the world is crazy and the way my brain's seeing it is so inconsistent and it does just make the world seem a mess. I have a general sense a lot of needing to do something to fix it, or it'll just fall apart worse, but I never know what.

I've been having especially bad trouble grounding myself lately, too. One thing that helps me is going through the senses one by one, kinda doing what I think some people call body scan meditation. It also helps me to find certain mantras to tell myself when it's bad - self affirming, grounding, whatever I need. I've read one a lot of people use for dissociation, "I am here, here I am," but I don't know if that one helps me much personally.
It also really helps to remind myself sometimes that it's only a change in my brain doing this, and that it's temporary - the world is still there, working the same way, it's the same world that seemed more normal to me and made sense before, and it will again. I'm still me, I'm here, and I'm experiencing some problems but they will pass, and these feelings, even if unpleasant, aren't actually dangerous and technically can't harm me.

I hope things get better for you soon.