At what point is a negative pregnancy test considered conclusive? started my period but still worried about pregnancy. tested negative 11 days after possible conception. trust the negative or test again?

Home pregnancy tests are very reliable about a week to ten days after a missed period... not related to date of conception. If you truly had your monthly menstrual period, your uterine lining has been shed and you are not pregnant.

Testing "negative 11 days after sex" may not be reliable, and onset of bleeding may be secondary to a pregnancy outside the uterus (ectopic). A serum HCG test can detect even low levels of pregnancy hormone and is very accurate.