rolling stomach pain

For the past 2 days I have had  "rolling" stomach pain. At times my saliva overacts and I fell like vomiting, but it doesn't happen. The pain starts at the top of my stomach and will roll down to the bottom. The pain is like a knife. It comes and goes every ten minutes. At first I thought it was the flu, but have no symptoms. I do have some constipation and at times strain to have a bowel movement. I cannot get a doctor appointment until tomorrow. Thanks for your kind attention to this matter