What Causes Frequent Headaches And Back Pain After A Depo Shot?

I was on the depo shot for two shots. I did not have my period again for 5 months. then I had my period, dark brown blood, about 3 or four times regularly. Now i have not had one for 9 weeks. I feel like i am having pregnancy symptoms. I get frequent headaches, heightened sense of smell A LOT, back ache, not very nauseas, just with certain smells, I am constantly tired, mood swings that I can not explain, my emotions are all up and down, and just a week ago i noticed more vaginal secretions, they're clear and in high amounts. I don't know if it's an effect of coming off the shot. But I have not taken a pregnancy test yet, I just thought i would get some advice first.