After the GB surgery, the bile flow may be unregulated as it flows from the liver to the duodenum. You can ask your doc if you can try something like a bile-binding resin (possibly Questran or Welchol).
If you have gastritis, about the only thing your doc is going to say your stomach will be able to handle will be tylenol. It's not suggested that you take any of the NSAIDs like advil since they can also cause stomach issues.
Also consider following a GERD friendly diet. You can find a representative example of foods that are good and bad at www.gicare.com.
So, because your gallbladder is not functioning anymore (its not there right?) than you have bile flowing...it is not being directed to the intesines...I know a girl who has the same problem...there are certain foods that make it worse than others. In your case...alcohol, asprin and pain killers are things you can not take comfortably. If you have to take them...than you will have to determine what is worse...the bile or the pain. Would something without asprin such as advil or tylenol work better or would it do the same thing? Alcohol...you can live without unless you are an alcoholic. I am an alcoholic...I don't drink now..but when I was in the active phases of drinking...I would chose the drinking because you get smashed and you don't feel pain...but then you have the bile. If you can stop drinking...and switch to other pain medication until you find things that work better, that would be the best answer.