Another cause of abdominal discomfort
during pregnancy is related to hormones. The
pregnancy hormones can also slow down digestion. This causes gas, bloating, and adds to that overly full feeling.
If you are experiencing contractions at 28 weeks, I would recommend speaking with your doctor. It may be just the Braxton Hicks contractions, but it is better to make sure. I don't know if your stomach discomfort is related to the contractions, but make sure to mention that as well.