I think I might be pregnant HELP!!!!!

Ok I had sex with my coworker a couple weeks ago and we didn't use protection I mean I did ask but after a few things started happening I didn't even think about it anymore.....stupid right? We had sex on the 16th and with the help of the lovely <a href="https://play.google.com/store/apps/details?id=com.glow.android">GLOW app</a> reminding me I was supposed to have my period on the 30th. My period log is never incorrect so I'm getting worried so bad that yesterday I purchased a home pregnancy test. The test was negative but my bestfriend and my cousin both said I did it wrong. Is it too early to determine pregnancy right now or did the sex just push my period back? HELP!