Uncomfortable feeling down left side of neck/throat, swollen tonsil on same side with whitish spots coming and going on the tonsil. what could it be?

Tonsil spots: I assume you do not have a fever or other systemic symptoms? These can be tonsil stones and are benign but uncomfortable.

Tonsilitis: Pharyngitis or tonsilitis. See your doctor for treatment.

Strep Throat: It surely sounds like a serious infection such as a strep throat. I would advise getting to your medical clinic.

Many things: A multiplicity of medical and dental problems can be causing your signs and symptoms. See both your physician and your dentist for evaluation and rx. You have to be seen to be diagnosed, can't do it over the computer.