I Get These Cramps Right Under My Right Ribs. It's

I get these cramps right under my right ribs. It's happened occasionally for years. Now it is happening all the time. It's not that it is real painful. It just grabs and I cannot hardly move. Standing and stretching helps, but sometimes I cannot sit back down comfortably for a while. It's starting to be a problem. I walk about 5 miles a day and am an active person. It always happens when I am inactive, like sitting.