HELP! Please Read

Munchkin woke up with a rash on his belly and neck yesterday. His back was lightly affected too, but not badly. This morning his rash is worse and has spread to his limbs, it is almost as though I can see it spreading before my eyes. Munchkin had a tough time sleeping last night, he woke a few times fussing. He was fighting me when I tried to pick him up, as though he was in discomfort. I helped him by giving him baby tylenol. He isn't displaying any other symptoms like fever or diarrhea, so I am confused.

My initial instinct was to take him to the Dr.'s office or insta-care, but my parents and husband insisted that it is nothing to worry about. My mom thinks that it might be a prickly heat rash. I couldn't put my anxiety to rest and proceeded to drive my husband crazy.

I called the nurse at my Dr's office yesterday and was told that a rash can be caused by an allergy or a virus. We have introduced him to whole cow's milk and eggs within the past week. He has been on an antibiotic of amoxicillin, just completing the doseage today. He had a bug bite on his cheek a couple of days ago. It makes sense that it might be an allergic reaction to something, but what?

I am asking anyone who is a parent, has parents or knows a parent to give me some advice. Has anyone ever seen anything like this? What action should I take. Please Help!