Talk to Gastroenterologist on Pain In Upper Stomach Area That Comes In Waves

I had pain in my bladder due to which i took pain killers 3 times a day for one day (ponstan 500) and next morning i took one synflex 500. after that i got severe pain next day in my upper stomach area. the pain comes and goes. it also feels like waves. what could this be? is it side effect of pain killers? or do i need to get checked. i feel it usually in the morning when i wake up and then during the day the pain is not nearly not present but its been 2 days.