Help!!! Opt questions!

Been TTC for almost a year for our 2nd, I'm on cycle day 20. By glow, I'm suppose to have AF Wed Dec 3rd... Took a pregnancy test this morning. Got BFN. Having cramping, discharge clear but gushy, extremely tired. I'm taking OPT's twice a day. And I've had 5 so far. What is up with that? 11/18, 11/22, 11/25, 11/29 and today. So which day of O do I go by??? When I go to test for preg.