I posted on here about a year ago about my cat Levi when I came searching for some answers. Here's a quick background: He's about 8 yrs. old, indoor only cat. About 2 years ago, he started pooing outside his litter box. At first it was just right outside it, then in the same room, and it was in the basement that is unfinished so we just dealt with it, vet thought it was behavioral. Then it got worse and was happening upstairs on the carpet, on rugs. That's when we started looking for answers. He was checked for parasites last spring and had two different kinds. Did the treatment and got him rechecked and they were gone, but the problem persisted. Vet suggested an expensive line up of tests that we couldn't afford at the time, and also suggested Hills Prescription ID food. I was starting to look at better foods for both cats (they were previously just on Purina Indoor dry, which vet said was fine). I didn't like all the grain and junk in the Hills, so I tested out various other wet foods (gradual changes), and settled on By Nature, as the ingredients looked good, it was the most affordable, and the cats liked it. Then gradually switched over the dry to By Nature adult formula as well, which they eat but are not as big of a fan of. I give a little bit of wet in the morning and at night, and leave the dry out all day for munching as they are always bugging me for food if it isn't out.
The problem seemed to get better. Instead of daily accidents, it was only weekly or bi-weekly, and all near the littler box. Then, I was running out of the By Nature dry, and there was a good deal on Harmony Farms Indoor dry, so I thought I'd try that. Not sure if that aggravated things but now the problem is full blown again, daily messes all over the house. Sometimes its hard, other times its runny, and recently there has been drops of blood in it. He also was vomitting some, but that actually seemed to decrease after I weaned him off the Purina dry. Before it was actual chunks of dry food coming up, now its just little bits of clear liquid, maybe once every 2-3 weeks. He also yowls and cries when trying to poo sometimes, or he'll act like he's going in the litter box, but I don't see anything come out, then awhile later there is a mess somewhere else in the house. Oh, he has lost weight too, he's about 8 lbs. right now.
So, took him to a new vet because I felt like I was getting blown off by the old one. Scrounged up the money for a battery of bloodwork. All bloodwork and stool sample testing came back fine. New vet things its either food allergy, or IBD. He's leaning towards food allergy and wants to try new food, as well as metronidazole for a few months. He wanted to give him a prescription hydrolyzed food (not sure of brand), but said its OK if I want to try OTC foods first as they are a bit cheaper. I found that Natural Balance and Nature's Variety both carry limited ingredient foods. He said the best bet is rabbit, but he worries that makers are going to stop carrying rabbit in the future due to limited availability, anyone know of that? He said duck is too close to chicken, venison is too close to beef, and he would stay away from lamb because its not as easy to digest. So, if I'm looking at rabbit, that leaves me with the Nature's variety, both wet and dry come in rabbit, at least on the Petco site, which is where I'd be buying it in the store to try it out. But wowsa, this stuff is a lot more than the By Nature! I think my cat is going to make me go broke

I love my cat but we're pretty much a one-income household and hubby isn't rolling in lots of money
So, any thoughts on the above suggested therapy? Is Nature's Variety good, or are there any cheaper options to try? And not sure if I should try wet or dry or both. I started using wet food to give him more water in his diet, thinking maybe the problems were constipation. He eats both, but seems to prefer the dry, but maybe he's having a harder time digesting the dry than the wet?
Any other ideas? I asked about cottage cheese as I saw it referenced a few places for runny stools, vet said it wouldn't hurt him if we tried it but he has no experience with it.