First relax. Do not get over worried.
Today is 3 rd day of fever
. Since you say he has rash
etc, it may be Dengue/ any other viral illness.
In dengue platelets start decreasing only after the fever subsides and other complications too happen only after the fever subsides that usually happens after 4 to 5 days or so.
If your child can communicate, ask him if he has headache/ eye ache/ severe muscle aches/ pain in tummy. These may favour the diagnosis of dengue.
There is a test called NS1 antigen test which is used to diagnose Dengue early than any other tests.
In complete blood count
usually dengue cases have low total white blood cell
count. This low WBC count
or Total leukocyte count also favours dengue.
And all cases of dengue are not serious. Even the serious ones if managed well do not end up in problems. So relax, approach your doctor for NS 1 antigen test, give adequate fluids and rest to your kid, keep a close watch on his health.
Wish a speedy recovery for your kid.