pregnant?

So I really need some help. I've googled like crazy and I'm still, maybe even more, as confused as I was. So I got my first depo shot in December, but I wasn't able to go back and get it when I needed to. I started my period back on May 2nd and it ended on the 6th. May 27th my fiancé came inside of me and I'm super worried I could be pregnant. My period is due this week and I'm feeling cramps, but nothing has showed. I've read that cramps are apart of being pregnant too. My breasts don't hurt and I read that was a big sign if they did. What are the chances I'm pregnant? And when should I take a test? I really want to take one now but I don't want it to be to early and get a false negative. Please help. Thanks in advance!