like MiffyMiffy said, you could have ovulated late this cycle. Generally, you tested positive later than expected is probably because your HCG count (beta level) is low. HCG is a hormone produced by the placenta once the fertilised egg attached itself to the uterus linings. Generally, HCG count doubles every 2~3 days. In the case of an ectopic pregnancy, HCG count is either very low to start with, or it doesn't increase as rapidly as it would have in a normal pregnancy. If you are concerned, consult your doctor and ask about the HCG level. Repeat the blood test for HCG 3 days later. Your doctor will then know if it's an ectopic. ANy bleeding or shooting pain in the lower abdomen?