thurdsday dinner time I ate 1/2 lb .of already cooked shrimp...(supposed to be fresh)....within 15 min I had SEVERE stomach cramps, shaking , dizzy and s hortly violently vomited twice. Thought I would experience diarheaa very soon, but it was black tarry stool.........took some pepto and cramps stopped. Felt weak..went to bed...the next day, felt just OK....but now, Saturday...I have off and on stomach pains, watery diarrhea, with no warning....(previously it was ok).......I did not go to the ER............but wondering if I need meds.