Yes, it does seem that many of the diabetes meds affect the stomach. With your doctor's approval, maybe you could take half the 500 Metformin with a morning meal and the other half with dinner. See if that's tolerable. Food seems to tame the effects. Don't jump ahead too fast thinking about
insulin because you may not need it. If you're still producing insulin naturally, using insulin will not help your blood sugar if you're insulin resistant. How's the exercising coming?