My Son Has An Autoimmune Disease (PANDAS) Recovering For 2

My son has an autoimmune disease (PANDAS) recovering for 2 years taking Antibiotics, IVIG monthly. His disease is caused by strep infection, but he has never had strep throat. He is now having a sensation that when he opens his mouth wide the back of his throat feels like it has a cut. We have just had him tested for strep throat and it was negative, so we did another and it was negative. They also sent the test to be cultured.