Hello, Borislav.
It sounds like pouchitis. Your frequency of 12 - 18 times, gas, itching and soreness. Is it possible to call your doctor and tell them you are suffering, and request to move your pouchoscopy appointment to May or June? September seems too far away. There is no reason to suffer, and your doctor's office can try to find room for you, perhaps move a patient who is not as urgent or in pain as you.
When you feel gas but you are afraid it is stool, just get to the bathroom quickly and go. At least you will relieve the gas pain and the pushing. Sometimes when gas moves around inside it is very painful and the need to go is strong. Don't try to hold it. You'll make it worse by keeping everything in your pouch. Just go to the bathroom. If you are away from the house, always keep a package of moist paper towels or baby wipes with you for cleaning in case of accidents. We've all been there. It is distressing. You are not alone.
Can you give an example of what you have for breakfast, lunch, dinner? Your doctor said you can eat anything, but with the problems you are having you need to stop eating certain foods that cause gas, frequency, burning, itching. For instance, I cannot eat cabbage because it will cause frequency, burning, gas.
I do not think your reversal in January caused the problems you are having now.
I would stop taking the pain killers if you are not in pain. The pain killers will not stop the itch or gas or burning. You have to get rid of the cause. Pain killers can make you constipated or give you diarrhea.
Have you tried Metamucil to make your stools more firm? Firm stools are better than watery stools. Watery stools can leak out (you might not feel the small leaking). That liquid can hang around your bottom and cause intense anal itching and burning. Can you give an example of the foods you eat for breakfast, lunch and dinner?