I Am Suffering From Acute Rheumatic Fever, I Have Been

I am suffering from acute rheumatic fever, i have been injected by pencillin g benzathin 1.2 million every month, this time i was not having any pain in joints but when month was completed i got injection, and after that i got pain in joints like my knees, elbows and finger joints, moreover my urine has become dark as tar. Whats the reason