why do I keep getting negatives?

Dian • Married to the love of my life. Expecting our first baby March 2018❤️
So my period is a few days late. I know it should have been here by now. I have multiple pregnancy symptoms( super tired, headaches, dull cramps much different from pms, lower backache, etc) plus the feeling of just "knowing" but hpt keeps coming up negative. Could it still be too early? Glow said to take a test today so I took a cheap one from Walmart as soon as I woke up. Could I be doing something wrong? I'm not stressed or anything and even when I am super stressed my period doesn't take this long. I'm just kinda like where are you bfp I know you're there?