You've already said you're going to the Doc which is obviously the first step.

As a PT, I have to know a bit about this stuff but organ function is definitely not my field. Having said that, from additional training I've taken I would guess that you may have an ulcer or you may simply have muscular tension/adhesion in the abdomenal wall. It's muscle too and suffers from all kinds of muscular aches and pains just like skeletal muscle. Usually it's secondary to old scar tissue that is adhesing muscle fibres together and impairing the muscular motions of the stomach. That could explain the chewing thing, as you chew, the muscle activity in the stomach changes in anticipation of receiving food. It would be like loosening up muscles in your legs with a light bike ride.

So, go see the doc but I'd also look into finding a massage therapist or physical therapist that does visceral manipulation. I just took a course in this and it can be amazingly effective for abdomenal pain. It would also not be contraindicated even if you have an ulcer or some other process going on. They are very gentle and safe techniques.