B.W.
This doesn't sound like chicken pox to me and I had it bad when I was a kid and then had both of my daughters vaccinated for it when they were toddlers. This does sound like a virus of some type. I say this because viruses have the lovely ability to ebb and tide each day and they morph into new synptoms just when you think the whole illness is about to take a turn for the better. If your son does not have a stuffy or runny nose, no ear ache, no sore throat or tummy pain.....than if this is a run of the mill virus, it needs to be gone very soon or you need to take him into the pediatrician and have him looked at. My rule of thumb is this...I will treat and watch a fever or illness symptoms for three days but if other things like ear pain, sore throat, vomiting, rashes, or anything else starts cropping up, we are off to the doctor. If the fever presists past 48-72 hours or it is high....we are off to the doctors. I'd rather make a visit and have it be nothing than let something mysterious linger. I'm not a "OMG" type of mom at all, but I'm cautious when it comes to illness of any kind. Sounds like a virus and because his fever is up and down, it sounds like it's on it's way out the door although if it were me, I'd be sure that this isn't strep throat. The fever, sore throat and belly pain are a bit suspicious. Best to have it ruled out so you don't get sick, mom.