What Causes Intermittent Menstrual Bleeding Post Depo-Provera Shot?

Hi, I have a quick question, but it can t be fully answered using the symptom checker. To start, I am a 20-year-old female and I recently had a baby on Dec. 7th, 2016, so I am 4 months and 5 days postpartum. I got the Depo-Provera shot in February as my form of birth control. I had my period about 2 weeks ago and then it came back a week later and I am still bleeding to this day. The first time I got it, it lasted 7 days. But, now, the bleeding has lasted 10 days and shows no signs of stopping. I don t know whether to be concerned or not because the shot indicated that irregular spotting would occur; however, this is not spotting. Also, I have been have hair loss. I don t have any bald spots or a receding hairline, but I loose a decent amount in the shower each time. If you could get back to me, when you get the chance, that would be great. Thanks, Ali