Help!

So my son has had an on and off fever of 103 since yesterday morning.. I’ve been switching from Tylenol to Motrin and luke warm baths nothing is working. His fever goes down for maybe an hour and then comes right back in full effect! Now he has a little red pin prick rash that seems to bother him all over his back. My doctor is well aware and is seeing him tomorrow but does anyone have any idea as to what this is? He is taking fluids but has no appetite and he is not vomiting and no diahrea. Help me out!