Sure you can have gastritis with low stomach acid. It's caused by anything that irritates the stomach. Drugs ie asprin, ibuprofen, alcohol, smoking,spicy food. Having high acid levels would make symptoms worse. If you have had it before it is highly likley you will get it again. Sorry for the bad news! Do you have to lie down a lot? That wont help. Try putting a couple of books under the head end of the bed to tilt it very slightly- that will help to prevent any reflux and might get rid of the bad taste in your mouth. Ever been tested for helico pylori bacteria? That can cause chaos in the GI tract. What you say about the low mood ect in connection to the gut. Yes that comes up a lot but it does'nt always mean you have to take stuff to fix things. Getting rid of gastritis might be enough. Woof to your dog!