Diahrrea? Please Help?

Hello, IDK if this works but ill give it a try

Hi my name is eric and my problem is diarrhea. I get completely unprovoked cramps followed by diarrhea. First i thought it was stomach or colon bacteria , got tested it was fine. Then i figured out that it might had been amount of coca cola i was drinking, which still appears to be the cause after i drink about 1 L a day, cramps start and diarrhea after it. But in some occasions like today, i have uncontrollable urge to drink liquids, example yesterday i drank 2L of water at least, even though i didn't sweat or work or had been on the sun. Woke up in 3.a.m. with extremely painful cramps, followed up by 5 hour diarrhea, connected to a WC, i could barely leave bathroom, even though i didn't drink a inch of juice or cola, only water. It seems to be over-hydration but why do i feel the need to drink even though i shouldn't?