A HPT is typically accurate about 14 days after conception. A blood test is a more sensitive test for pregnancy that you could consider.
i am in the same boat ....
somtimes we can skip a period for no reason at all,even if you are normaly regular.ask your doctor to do a blood test,hel take a blood sample and then another 2 or 3 days later to see if the levels have increased.as far as i know,there is no mistake with the blood tests,it will tell if you are pregnant or not.hope this helps good luck xx