Bingo, smart people here......and great advice. The steroids helped you feel better quick as the one physician started you on the steroid right away.
My son had mono at your age and he also had the strep throat too. He was very ill and finally ended up in hospital with the IV for fluids and steroids. He missed his graduation party. So I would believe that you have it and take care of yourself.
Check back with the Doc about
your activity and your other concerns. Hope you stay feeling well.