Help!

Hey everyone. So I had light "spotting" and then it turned to dark discharge, this happened 2 weeks before my expected period was due. It lasted about 7 days then was gone. Well my period comes around the 17th-23rd every month but it's the 30th and I still haven't gotten it or even felt like it was gonna come other than light cramping but nothing like usual. On Monday the 27th, I took two of the first response pregnancy tests but they both were negative? I don't get it. Has anyone had this occur and turned out to be pregnant, and if you weren't pregnant and this has happened to you, do you understand why? HELP!