Don't know what to do anymore, please reply

I've tried posting numerous times on numerous rooms on the app and I'm getting no advice/ support whatsoever. 
I've posted because AF is 19 days late, where I am usually regular 28 day cycle, but pregnancy tests are coming up negative. Any advice would be greatly appreciated, going out of my mind. Is it still possible that I am actually pregnant and just not showing on hpt, or time to let go? Doc appointment on the 16th.