Welcome to HCM!
Yes, most likely its gastritis
Take syrup gelusil
, cap. ilaprazole with your doctor's advice.
Avoid taking pain killer medication like diclofenac
at so late nights, also avoid sleeping at so late night.
Get examined by your doctor once, if pain is extremely severe, your doctor may give you intravenous PPI.
Wish you a pain free time & good, healthy life.