I was diagnosed with tonsillitis but after going on antibiotics, i am starting to develop sneezing, alternating runny and plugged nose, and coughing.

Tonsillitis: I was diagnosed with Tonsillitis but after going on antibiotics, I am starting to develop sneezing, alternating runny and plugged nose, and coughing. ANS: unless you had strept test no good reason to be on antibiotics for tonsillitis as most likely virus. And sounds like a cold (virus) so abiotic won't help. Strept tonsillitis usually does not have sinusitis. So tough it out or see Dr again.