Severe acidity. Stiff. what should i do!

I have undergone kidney transplantation 27 years back and bypass surgery 5 years back. I am on regular medication for both these conditions including steroids. I have a very regular and restricted diet with no fried or spicy or non vegetarian food. I am also a teetotaller. All my blood parameters are normal and do regular follow ups. However last one year I have severe gastric issues but with no pain in abdomen. It is a heavy burning sensation through my digestive track and stomach. The issue persist severely in the morning hours and I also have issue of constipation. I drink around 3 litres of water a day. I am taking ranitide 150 at HS. Every time i get this issue it makes me tensed, depressed and very tired. I used to walk regularly but since this problem i am not able to walk and also have my left shoulders stiff. What should I do