please someone can help me?

Last week my brother& grandma were both having horrid stomach pains, constant diarrhea & vomiting. This week since monday night I've had bad sharp stomach pains and nausea but no diarrhea or vomiting .. but yesterday i was feeling perfectly fine and eating foods i felt great ! Now this morning I'm currently hunched on the toilet with diarrhea every 5 minutes and i have worse stomach pains & nausea..please help me I'm so confused and i feel like I'm dying, did i get it just now or have i had it all week?? I'm 15 if it helps & if you know of anything to help with the pain or diarrhea or anything please help me and let me know please! :(