Hi all, this is going to be a fairly long post but I really could use some help. I have a 15 year old tuxedo male cat named Zinger. Recently as in about a week ago my husband and I brought home two 2 month old kittens. We have had in them in our spare bedroom basically sequestered since we brought them home. The first three days or so we'd occasionally and very slowly introduce the kittens to Zinger by having the kittens in a crate in the living room and letting him look at them or by holding a kitten in our arms a decent distance away. He was definitely not super happy about them (hissing, growling) but for the first three days he was still functioning normally and eating. However since last Wednesday, he's basically stopped eating. We've been giving him Hills K/D dry food since Jan 2021 after the vet told us his creatinine in his kidneys was getting high and he has enjoyed the food. However he downright refuses to eat it now. I took him to an emergency vet on Friday (7/30) after he had vomited white foam twice and they did blood work, his creatinine was on the higher end but the vet didn't think it was enough to cause major kidney disease yet. They gave him a Cerenia shot for nausea, some fluids under his skin and gave us Mirataz for appetite stimulant. I rubbed the Mirataz on his ear as directed and he ate like 3 or 4 treats but still wouldn't touch his Hills K/D. I tried to offer him some wet food on Friday and he really didn't want it. Then on Saturday, I got him to eat a very small amount of wet food in the morning but that was basically it. So yesterday (Sunday 8/1) my husband and I took him to a different emergency vet and they did another exam of him (no bloodwork this time) and an X-Ray and said basically everything seemed unremarkable aside from a slight fever of unknown origin. They offered us another appetite stimulant to try (Entyce). The weird thing was that while we were waiting in the car for the vet he was again eating a bunch of treats and when we got home from the vet after administering Entyce, he did salivate but then he ate a decent amount of Tiki Cat wet food. After that however he basically went into our home office and slept on the desk chair for hours. Last night, he looked super out of it and severely lethargic but as he's been doing the past few days still slept in bed with us as normal. This morning he vomited yellow bile outside of his litter box and to my knowledge he has not pooped since Friday morning and that was in my car while waiting for hours for the vet. Shortly after this, I offered him some of his treats and he again would eat those but when I offered him his Hills K/D he just sniffed it and wouldn't eat it. I gave him another dose of Entyce and some Mirataz on his ear but he wouldn't even touch any wet food this time and salivated/foamed even worse. I'm just at a loss for what to do now, I don't know if he's truly sick or just stressed out/depressed from the new kittens - though we've kept them in their room away from him since he's stopped eating to limit his stress. I don't know if the appetite stimulants are even worth it anymore as they don't seem to really help. I am going to buy some baby food and some cat nip treats today to try and help but honestly I feel like he just keeps getting nauseated over and over again and does not want to eat. The vet trips have cost us nearly 900 dollars in two days and while the money is not a real issues right now, it's just frustrating as it doesn't seem to be getting much better.