Could my stomach ulcer be the cause of my weight gain, (and inability to loose it) bloating, burning upper stomach, constipation, and dhiarria?

No.: Ulcers don't cause weight gain, although they can certainly cause burning in the stomach area. Bloating, constipation and diarrhea are likely separate from the ulcer. Any time i hear this many abdominal complaints, what comes to mind is the probable need for dietary change, at the very least. You could have irritably bowel syndrome or several other problems as well. See your doctor.