Reasons for a Negative test after I’m 16 days late

I always have a regular cycle.. every 21/23 days.. my boyfriend and I had sex 1 day before my estimated ovulation day.. I’m not on birth control I never have been... we don’t use protection & he does not pull out... I’m now 16 days late, I’ve tested 3 times each 5 days apart and I’m still getting negative result each time.. I’ve never had a late period & have not had any drastic life changes recently