Uncomfortable feeling in upper left abdomen?

ok so this may be a little long and im sorry but if anyone has any ideas or tips i would really really appreciate it..about 2 months ago after i had taken my dog for a walk i was sitting at my desk and gotten a ache/discomfort in my upper left side/abdomen area..i brushed it off and just thought it would go away..about 3 weeks went by and it still had not gone away..and my bowel movements had changed..so after freaking myself out so much (i do have a panic disorder and usually think the worst) i went to the ER and they did a bunch of stuff...x-ray of the LEFT side, took blood and urine, did an ultrasound of my RIGHT side to check my gallbladder and kidneys..everything looked great..he did say my left side was very slightly swollen and prescribed me zantac and said to take it for 3 weeks before i go to sleep..well i take it when i remember..so it has now been 2 months and this feeling has not gone away..it just feels tight and just uncomfortable and when i have a bowel movement (im sorry) its really piecey?..i dont really know how to explain it..but i just know its not like it normally use to be?..i am going regularly though and their hasnt been any blood and i dont feel nauseous..my eating habits have changed some since ive gotten this feeling so it may be related to that? im sorry this is so long..but anyways..any idea of what this may possibly be?..thanks to anyone who takes the time to read all of this i appreciate it..