[canana]

I totally understand the frustration and helplessness like he's never going to get over the upset stomach issues. I struggled with this too at first with Scottie. It was really stressful!

How much time was there in between the changing of the Science Diet, Natural Balance, and then Royal Canine? Was this over a few days or a week or a few months? If his stomach has been irritated for the past 5 months, I would try not to change up his food again. Find a quality food, read the ingredients, make sure there's no cornmeal and that it's grain-free, and just stick to it. The best food ingredients say chicken or turkey or fish etc without the word "meal" (i.e. "fish meal" isn't as good as just "fish").

It took me a while to get a routine down with Scottie, granted he only had a sensitive stomach and no other diagnosed illnesses. Each time he had soft stool, I took away the kibble and he was on an oatmeal/boiled chicken/pumpkin mash diet. This is easier on his stomach than the hard-to-digest kibble. I'd feed this either a day or two (or longer if the bad/soft/diarrhea poop lasted). Note that when they eat this mash, there's much less poop because most of it is absorbed into their system.

When his poop solidified again, I'd very slowly start feeding him small amounts of the kibble again. If the poop was still good, I fed a little more kibble with each day.

I made the mistake of switching his kibble too many times initially. Mostly because he seemed to be disinterested in his food after a couple weeks. Then because of the switching, he got upset stomach. I learned from my own experience, to just stick with one kibble as long as his poop is good when he eats it - he'll eventually eat it when he's hungry even if he's being picky one day and refusing to eat.

It might be worth trying for you, but freeze-dried meals are easier on their stomachs than kibble. For a while when Scottie had upset stomach, I had him on the chicken/pumpkin/oatmeal mash and introduced freeze-dried meals in prior to the kibble. I just wanted to make sure he was getting enough nutrients because that mash is not sustainable over long periods.