I Think I Have A Really Bad Case Of Strep

I think I have a really bad case of strep throat. But the test can back negative and nothing I do will sooth the swelling or pain. My tonsils are extremely inflamed and covered in white. Recently my tonsils began to bless they started getting covered in black. I've had it for about 6 days and it's only progressively gotten worse. Im in a lot of pain and I'm curious to know if it could be something else.