vaginal pain and bleeding 8 weeks later??

By the time I was 5 weeks PP I had stopped bleeding completely. I'm breast feeding so I don't plan on getting a period. For my 6 week PP appointment I got the depo shot and my doctor said don't plan on getting a period because of it and breast feeding. Then she gave me a vagina exam and it hurt extremely bad and for over a week it still hurt really bad and was sore. I'm now 8 weeks PP and I started bleeding. Not heavy bright red period blood or any other symptoms of a period but dark red and more then just spotting. Why did I start bleeding again? Side note: I haven't had sex yet still.