What Causes Crying Due To Discomfort With Body Rashes And Appetite Loss?

My 1 year old boy has no known allergies or illnesses. On saturday he started a fever and some vomiting I gave him acetominophen and pedialyte. It kept it under control but he suddenly developed a red rash all over his body. I took him to the emergency room, they told me it was a mild virus to keep on the same treatment I was already on and that the rash was the fever itself. By day 2 the vomiting stopped he ate normally but the fever continued. By day three the fever stopped and everything seemed getting better. Now it s day four he has no fever and no vomiting but he doesn t seem to stop crying (like he is uncomfortable) or sleep well and he has a rash again in his body and he has loss of appetite. Should I be concerned?