Pain under left ribs. Advice on this.

Hi,Doctor I have been having occasional pain under my left ribs after eating something fatty.Its not like I always feel the pain after eating something heavy but sometimes I do most commonly when I eat a pizza.This has just happened once or twice.The pain is very dull and mild with no other symptoms as such.Does not disrupt my daily routine goes within a day or so.And it all started when I took an ipill.The next day after taking that pill I had this pain which lasted for several days and then it became fine.It might not be related to the ipill but just to give you a clear understanding.The pain is not very sharp.A lot of People have adviced me to drink plenty of water and to avoid heavy food for sometime.i wanted some advice on this.