Hi A.,
(HUGS) I know, as I am sure every other mother knows, how hard it is when our kids are sick. One thing I have learned is that you know your child the best. Call it a Mother's Gut instinct, but if you are truly concerned, I'd go to another pediatrician. Get recommendations and if the doctor doesn't seem to be "listening" to you, find another one.
In my case, my kids seemed to get more illnesses after turning 3. I swear they would alternate between virus' and strep, so I never knew and had to take them in. Their fever temps would be higher, though the fever itself isn't dangerous persay, it's what it is fighting.
One other thing, when they swab for strep do they do the rapid test and then send it in for thorough analyzes? My kids have failed the rapid and sure enough I get a call a couple of days later with it being positive. Also, if the nurse isn't doing it correctly, she can miss or contaminate the swab causing it to be a negative.
Gosh, there are so many different things, just ultimately, you are the mother and if you feel that there might be more wrong, definitely have her checked out. I would suggest writing everything down (her symptoms, when they occur, what she was doing before, how long they last, etc.)
Good luck! Keep us posted!
K.