I had a bad reaction to depo when I was 16. I bled for a month and a half straight. It's just the way it reacts in some people's bodies. I was also sore and very moody. The bleeding was the worst part...period for a month and a half! But all tests had come back normal. It was just the way my body reacted to it. You should definitely try a different birth control and skip the depo when the 3 mnths is over.
Didn't Dr say anything!!!! Depo can make things more sensitive. Less lubricated. It's hormones so it can make you depressed, whiney, cry, mad, spleep, happy, headaches, cause acne- everywhere. But after the speed bumps getting on the road you're good for 3 months. Some people bleed with their normal period times at first. Lessening with time to no period. But I'd definitely go back if still bleeding after the 3 days. Take the ibuprofen like Dr said. Read about the drug. It has good and bad things. Educate yourself so you will know whether you need to be scared.