Pregnancy

When taking a test .... Do you go by the fetal age . when I calculate when my due date would be if I am pregnant . it says 4 weeks pregnant but the fetal age is 2 weeks . .. So should I wait another week until the fetal age is 3 weeks to take a test ???? Im soo confused .... I am 5 days late for my period ... Swollen feet ... Breast a little tender .... Appetite up and down ... Please help ..