I have a really bad cough and a lot of phlegm ever since my tonsillectomy. what's wrong with me?

Cough and Phlegm: Maybe it is residual inflammation from the tonsillectomy? Maybe you are just noticing more cough and drainage because the tonsils are gone and you have allergies allowing more mucus to drain down your throat and cause cough. Removing the impediment of tonsils can make allergies more apparent. More drainage. See your allergist for testing.

See you doctor: Cough and phlegm can be caused by many things. After surgery you are at an increased risk for a pneumonia (particularly an aspiration pneumonia.) sometimes worsening acid reflux, asthma, can cause these symptoms as well. Most importantly you should see your doctor to rule out pneumonia.

Depends: It depends on how long since the surgery. The surgery is performed under general anesthesia and the endotracheal tube can lead to some irritation of the vocal cords and trachea. Also, there are some minor salivary glands associated with the palate, and the loss of lubrication can be an issue. Finally the palatal shape and function may change after the surgery aggravating a post nasal drip.