Hmmmm

I was supposed to start my period on the 14th, of this month and now it’s the 22nd. I took a pregnancy test 3 days ago, and it came out negative. I’m not cramping or anything that makes me think that I’m about to start my period. My lower back started hurting today but that’s it. Could it be that it was too early to test, or that it was a faulty test or maybe I’m just not pregnant?