What Causes Constant Pain In Lower Abdomen?

I am 69 year old in fairly good health. I am allergic to gluten. I take blood pressure pills and have a thyrhoid pill daily. Lately I have been suffering with lower stomach pains. A week ago I had a large coffee while driving home. When I reached my destination after a couple of hours driving I had a very severe lower stomach pain. I rushed to a washroom and emptied my bowels very vigorously. Since then , * days Ive been unable to keep food inside me and have emptied my bowels several times after eating. There are no signs of blood in my stools although some are skinny indicating an obstruction. Sometimes i feel like there is a perforation in my large intestine as I can feel a cold feeling when i drink some fluids. What do you think Tom