I have had gnawing stomach pain at naval last five years since beginning coumadin (warfarin). Family dr. Says it is hard on stomach & could be the cause.?

Eval for ulcer. Coumadin (warfarin) by being a blood thinner can put you at risk for bleeding and of particular concern is the GI tract. Mild gastritis can turn into significant bleeding when u have a blood thinner on board. The symptoms u describe make that at least possible and should be looked into by your doctors.