You were not even 12 dpo on the 16th! That is waaay too early. You should wait at least till 13 dpo to test. Good luck!!!
Don't stress to much, it could just be too early, wait a couple of days and test again. Also If you are not patient ( i know i wasn't) you can also go to the Dr. and get a blood test done I got a BFP with that before one with an HPT. Good luck!! Lots of baby dust to you!