Help

[Charlottr]

Hello all, in extremely stressed out and I've paranoid about this. My last depo shot was in April 2015 so nearly a year ago, when it was due to have another one I didn't go back. So in June I started bleeding right up until December. I thought enough was enough so I went to the doctors to see if they could stop the bleeding and they gave me northisterone to try kick start my cycle and it worked. I had a withdrawal bleed in January and a period after that (same month) I then came on again 29 days after and had a normal period. However I'm now due again and I'm 6 days late for my period. We are trying to conceive. 2-3 weeks ago I had some pink spotting in my pants, not too sure what it was. I've done pregnantcy test all negative. I've been feeling sick and such bad back pain I can't even move. I'm extremely tired. Could I be pregnant even though it all negative at the moment.  

Sorry for the long post and thank you for reading :)