Gastritis and very very sensitive stomach

I am 69 and got covid in March, and after 8 months of functioning at ~50%, the long covid (LC) seems to have ended. it gradually tailed off, but I caught a cold from hubby in late October and LC was gone afterwards. Fast forward to a week ago and I got norovirus from hubby; dropped 4 lbs, nasty symptoms, extreme fatigue (it didn't initiate LC). He is in big trouble if he gives me a virus for Christmas.
I have had celiac for 14 years and collagenous colitis for 7; I knew what to eliminate from my diet when that hit because I've kept a food log for 14 years (I'm a scientist, we do those things). So, I went from just gluten free (GF) to also no NSAIDs, little alcohol, few legumes, and no cashews. Mostly a FODMAP diet except I can eat dairy, onions, and other. I had pelvic floor physical therapy after a bike injury; lots of folk there with ED, injuries, post pregnancy, and other. Below is a long list, should any of it be useful to you regarding GI tracts that suck:
1) Keep a food log, especially what you ate when you have a reaction
2) lots of small meals with time to digest between if there is GI grumbling
3) Eating enough fiber and drinking enough water. Psyllium as bulk husks or powder is cheaper than Miralax. Drink lots of fluid with psyllium or ground flax
4) Legumes may be better tolerated if fermented (miso, tamari/soy sauce) or if lower-FODMAP legumes soaked overnight and the water discarded (most oligosacarides are on the outside) or some canned beans.
5) Avoid NSAIDs like aspirin. They irritate the GI tract.
6) I eat few processed foods because I've become sensitive to more chemicals. Avoid if the ingredients list is too long.
7) Pelvic floor and aerobic exercises help to keep things moving. Walking, kegel and other PT help to strengthen your core. It is hard to exercise with LC so do in bits with rest between.
8) Check thyroid function with TSH and Free T3 and T4 bloodwork. Low energy could also be lower metabolism.
9) Get enough sleep and avoid stress. The GI tract has a pretty sensitive nervous system and stress hits it hard. Meditation and reading help to keep flares down.

I am sorry this is happening to you. I have a mostly hate relationship with food since getting Long COVID. Food can smell horrific. I have no idea what I can eat from one day to the next. Buying groceries is really difficult. I am lucky to have one meal a day which is sometimes really small and consists of plain noodles. I have SIBO and gastroparesis. I had gastritis. I stopped taking all Nsaids - ibuprofen. I have received several diet plans, some conflicting. Then there is the issue that I can't eat food if it smells like death. I have pain, cramping and lots of GI issues. I was prescribed Hyoscyamine for help with horrific cramping. I have learned that the gastroparesis is part of the impact of Long COVID attacking my autonomic nervous system. I take Cymbalta and Gabapentin for the nervous system issues. I do think these medicines have lessened some of the pain I experience. I sometimes have no idea if I am hungry or nauseas. Sometimes I am both. I eat and take anti-nausea medicine. I used to eat a really healthy diet and exercise. I can't do either anymore. My goal is to be able to eat something, regardless of what it is daily. I have horrible acid reflux. I take 60 mg of dexilant daily. It does help but does not fix. Sometimes I eat peppermint stick ice cream that I make to help with blistering in my mouth and throat and peppermint sometimes helps to calm my stomach. This has been going on for over 3 years. I had to give up worrying about the quality of food I eat. My Rheumatologist does regular bloodwork to manage my vitamins and minerals. When this first started, I ate bread or potatoes only, once a day, for 9 months. That was all I could tolerate based on taste and smell. Then to add insult to injury, I almost immediately gained 50 pounds. My weight now fluctuates up to 20 pounds a time. I don't eat or drink enough calories to have that kind of weight gain. I am assuming I have bloating and that part of the weight change is due to where I am in the cycle of gastroparesis. You fill up and then finally empty. I am taking citrucel tablets, can't tolerate drinking fiber drinks. This helps a little. Good luck. Again I am so sorry you have this. I hope you can find a way to manage day to day life in as positive way as possible. I am cynical about eating so if food smells good and tastes good it is wonderful!