I Had A C Section 8 Months Ago. Today Is

I had a c section 8 months ago. Today is my first time having a period after birth. My lower back is in so much pain. My stomach has severe pain also. I have tried walking it made it worst. I sneezed and it felt as if I had my C section all over ago. What could this be? I have taking Advil and it gave me no relief, I am using heating pads still nothing. Please help.