All the symptoms of pregnancy but negative test?

Okay well, im only 15 days late on my period. I know its early, but i swear about six days ago ive just started to feel like crap. I eat waaay more than i used to, way more hungry. I used to have like one meal a day and now im eating all the time. Also, i have insomnia, and i usually have to take sleeping pills every single day to be able to sleep, and now, i can just lay down and bam im asleep in five minutes without a sleeping pill at all! I took a home pregnancy test at walmart two days ago. It was my first pregnancy test ever, so i hardly knew how to use it, i was shaking because of how nervous i was, me and my friend walked around waiting for me to have to pee until finally i just made myself, so i doubt there was even enough on it. It said it took three minutes but it literally showed up about two seconds after i peed on it. Yes i read it right and everything. It was negative, but why else would i have all of these symptoms? Could it be wrong?