What Causes Heavy Vaginal Bleeding And Cramps While Walking After Taking Depo-Provera?

I have been on the depo shot for 4 years now and I never had any spotting or cramping. Last Wednesday I started cramping and bleeding a little bit. I also started feeling nauseous and felt like I was going to pass out. And i have thrown up. the bleeding stopped for a few days then came back but even heavier than before. I have also i also feel like im spacing out the bleeding and cramping only gets bad when I m walking around for long periods of time and it didn t start until last Wednesday when I was at work on my feet all day. Should I be concerned?