Pressure in Right side of Stomach. Goes.

Sir, I am experiencing fullness ONLY in right side of stomach as if if is stretched or pressure,  since last few months. It is not persistent, it comes and go...whenever it happens, it last for around 4-5 days and it goes...and again it happens... Consulted Gastroenterology, on first instance he gave me Nexpro 40, and told me to do 3 tests- 1) XRay Abdomen 2) USG Abdomen 3) Endoscopy with Biopsy I have done above 2 test Xray and USG Abdomen which came  Normal. Doctor is firm to go for endoscopy as well to rule out. Please let me know if it is necessary for endoscopy even if reports are normal If yes then endoscopy or endoscopy with biopsy. Pls let me know.. Also possible reasons for such fullness and strech in stomach right side.pls