Mk so here's the deal. I have two period trackers (glow and another one). The other one has NEVER EVER EVER predicted wrong and glow has only been off by a day ( normally start my period a day before glow predicts)., I have missed BOTH PERIODS predicted by my trackers. I AM NEVER LATE. Now before everyone jumps on me about taking a test, I did. It came up negative. Did I test too early or am I freaking out for no reason?