stomache aches for 3 months

For the last almost 3 months now, my lower stomach has been aching from mild to painful to diminished, but not quite gone. It does not hurt to palpate. Walking seems to increase the ache, sitting seems to diminish it. Everything else is normal, no other symptoms involved. It just seems like a normal bad stomach ache which should go away with a good bowel movement, but never does. Zantac, maalox has no effect, cutting out beer, alcohol, coffee, made a slight difference, but only temporarily. Really didn't seem to make a difference.