depo and feeling pregnant.

I have all these symptoms - cramping in the lower stomach, back. -headaches - boobs tender and nipple turning brown. - spotting Friday, and again on Monday. (About 2-3 weeks ago) -tiredness -feeling sick to my stomach -bloating I have done 3-6 home pregnancy test all came negative, and 2 blood test negative. The thing that is confussing me is depo symptoms are almost the same thing as pregnancy symptoms. And when I started depo I bled none stop for my first 2 ingections then 3 needle I stopped completely untill 2 weeks ago after I started spotting pinkish light brown blood (which I had with my first) I started pooring blood was that because my depo was trying to stop it and it couldn't hold back anymore? It's gone again after 2 weeks. I have headaches everyday bloating everyday and cramping everyday. Has anyone experienced this Please help