Still a BFN!

Even after the 4th test we are still negative! I am 45 days past my last period, or what I thought was my period because it was exceptionally light for being one. It was actually a spotter. Usually all of my periods are really heavy and lasts 4-5 days, this one that I had Came on November 9th and lasted til the 11th of that month. My last shot I received was sometime in August. I was only on depo for 6-8 months with a period every month and my last heavy one was June 10, 2014. All my early pregnancy symptoms, besides nausea didn't come until those dates in November. I still have the sore and enlarged breasts, having to pee every 20-30 min, my appetite is increased, my cervical fluid is abundant where I need to wear a liner pad, I'm constipated, and I have a heavy feeling in my lower abdomen. So my hpt still says BFN.