Doctor diagnosed me with strep throat today, put me on some strong antibiotics. i feel like i'm already starting to get diarrhea. should i be worried?

Strong antibiotic?: What do you mean by strong antibiotic? Do you know the name of it? All antibiotics can kill good bacteria that reside in the gut and upset gut homeostasis. This may lead to diarrhea although I wouldn't expect that to be due to the antibiotics until after 3 days or more on the medicine. In that case I would recommend clear fluids, and add probiotic.