Hi, My Baby Is 11 Months Old-last Monday He Started

Hi, my baby is 11 months old-last Monday he started getting blisters in mouth, fever, diarrhea,runny nose, just overall not feeling well at all-sleepless nights all week-took him to my pediatrician Wednesday, they said it was strep- gave anitibiotic. He has been on antibiotic, and blisters in mouth are better, but diarrhea is not, called ped yesterday with no openings for an appt.-we have taken to er this morning still with diarrhea, very worried about him dehydrating now, urine is not normal, very weak, not eating, not wanting to drink, they have sent him home with nothing. I am thinking now something else besides strep- not sure what- any suggestions - thinking seriously about another ER visit at another hospital-thank you