I (21f) woke up unable to pass a large hard stool and took milk of magnesia (30ml dose on bottle) to soften it, was that a bad idea? it started with a couple soft stools but then constant watery crampy stools all day long after, should i see doctor?

Milk of Mag is a laxative, not a stool softener. Laxatives stimulate peristalsis, the rhythmic squeezing, and relaxation of the muscles in the intestinal wall that propel the contents along. It is also the source of cramping. If your original problem wasn't due to a stomach bug then the effects of 30 ml of MOM will pass soon enough. Its important to drink tons of water to keep up with the diarrhea

The excess liquid store is most likely due to the milk of magnesia that you took, and that should resolve within a day or two. In the future, for occasional constipation, try adding more fiber to your diet and drinking lots of liquids. Good luck.