I can't believe people are confidently diagnosing you in postings on Mamapedia. "It's a cyst." "It's was just gas." "It was your bowel." "It was your gallbladder."
We. Are. NOT. Doctors. This could have been nothing (gas that is gone) or something (tumor, cyst, whatever). Minor or gravely serious. If it hurt so much that you were lying on the bathroom floor, even if it does turn out be just gas, you need to see the doctor. Even if it IS as simple as gas, you may have digestive issues that are serious if they're causing gas to be that painful. And if it's not gas-- wouldn't you rather know, so you can get treatment? I know you're scared to look it up and you were fine on the treadmill today, but why didn't you call the doctor the very next morning isntead of posting?
Sorry, but I don't understand the many, many women who post symptoms here, some far less painful that what you describe, and who seem afraid to see the doctor. Maybe they, and you, are scared to be told "It was nothing" and afraid they'll look silly to a doctor. But you pay for your insurance; use it, get what you are paying for, and who cares what the doctor thinks. Please get checked out for your kids' sake if not for your own.