Cat vomiting/not pooping

My 3 yr old cat first puked on the night of August 15th. I noticed after that he wasn’t really eating (usually his food bowl is empty after it feeds him and it was over flowing piled up.) I also noticed his gums were dehydrated and sticky so I put out more water bowls and he drank a little bit but not like normal. He also hadn’t pooped. He threw up twice on the 16th and I went to get him pumpkin/probiotics. He threw up 2 times 17th and still no poop. Finally the 19th he popped after I kept giving him pro biotic. Then he seemed fine the 20th - 23rd and was pooping normal again. Stopped the lethargic behavior. And in that time I started to notice his pretty litter was blue (possible UTI?) Then for the next 24hrs he threw up twice and his litter is still blue when he pees but he’s acting fine other than sleeping a lot but that’s pretty normal. He’s now eating. The vomit is never straight bile but it’s long enough after he eats that it’s not like whole chunks of food or solid or anything. It’s a pile of digested food. While he tends to nibble on things he shouldn’t He has never thrown up an object like a fake plant or something. Thoughts on whether I should be worried? Next steps? Last emergency vet visit (for getting into Lily’s) was $6k… so I would like to make sure I have done what I can at home first.

Hello - I had to look up pretty-litter, so for the benefit of anyone else reading this, it is a cat-litter that turns blue in the presence of alkaline urine.  Urine that forms crystals can be alkaline, so this can act as an early warning system for crystals.  However, it's also worth noticing that vomit is acidic and than on-going vomiting can reduce the acidic H+ ions in a cats' blood, thereby reducing the acidity of the urine (to compensate), and thereby also cause alkaline urine.  So it's possible that you may be seeing a consequence of the vomiting there, not the cause.    More to follow

So you seem to have an intermittently vomiting cat, who is not - as I understand it - showing any clinical signs of cystitis at present.  If they are showing signs of cystitis, the plan would be different.  I would indeed be concerned about the vomiting though.  Sometimes cats do vomit if they eat something they shouldn't and life goes back to normal again.  But if this is recurrent, I would wonder about problems such as liver disease, pancreatitis and so on.  There is a decision to be made about whether your cat is having an emergency in the immediate term - please do ask for triage by the vet if there is any doubt.  It sounds as though investigation as to the cause of intermittent vomiting, declining food and pauses from defecating my be required.