Depo-Provera while possibly pregnant?

So, I had sex about 1 week prior to my first (and last) depo shot. My doctor tested me before giving me the shot, but of course, it had only been a week so the test was negative. I got the shot almost the last week of February, 2014. The last few weeks of march, beginning of may, I began to feel very nauseous around various smells, and wanted to throw nearly everything up. Lately, I have been gaining weight, but mostly around my abdominal area.. my lower back is killing me, and I am clearly having pregnancy symptoms. However, I have taken two home pregnancy tests, and they have both turned out negative. Granted, both were taken at night, if that really matters..
What are the chances of me being pregnant? I have heard that depo provera can cause symptoms of pregnancy, if you miss a dose, or choose not to take the shot anymore.. but my symptoms started while still on dp.
Even though I have received two negative tests, is it possible that I am pregnant? I was due for my second shot almost 2 weeks ago. If the drug is still lingering in my body, could it produce a false negative? What other thoughts do you have?

Thank you for reading