2 days late but negative test

So I’m currently 2 days late no sign of it starting at this point. I had very light brown discharge Saturday only when I wiped real hard (I was trying to check to see if I was starting) and was supposed to start yesterday. I have never been late before on my period it’s like clock work, if anything I start 1-3 days early.

So I tested this morning with First response and got a flat out negative so idk what’s going on. Has this ever happened to someone before???