Pregnant on Birth Control???

Hey ladies! Here's a random story. I had been TTC with my ex boyfriend for 2 months. Right after I broke up with him the next day I went to the doctors to take a pregnancy test and it was negative. I got the Depo shot while I was there. The last time we tried was on the 19th! I went to the doctors on the 21st! So it's a possibility I took the test too early. Anyway I'm driving myself crazy because I think I may be pregnant right now. My doctor said If I was pregnant the Depo shot wouldn't harm the baby. Do you guys think that the Depo shot could have prevented implantation even after he already ejaculated since the days were so close? pregnancy tests have been negative but my body is acting crazy and I'm convinced it's just too early to tell. It's been what, 2 weeks and my period was super weird. Idk if it's the Depo playing tricks on me or If it could be a baby. Any similar stories?