Something Is Swollen At The Back Of My Throat I

Something is swollen at the back of my throat I cannot feel it on the outside, both sides of the back of my neck feel tender and painful when I turn my head, I find it really hard to swallow as it is really painful, I'm constantly spitting up saliva and phlegm as I am producing more than usual, I have a bit of nausea, chills, High temperature, blocked nose, mild headache. What could this be? I'm wondering if I have a case of tonsillitis?