If the endometrial lining is 11mm thick, it may be this thickness before menstruation. The most accurate way to detect pregnancy is to take a blood test for HCG, you can also use early pregnancy test or pregnancy test to detect pregnancy by urine test, around the tenth day after sexual intercourse, you can take a blood test for HCG to detect pregnancy. On the eighth day after the formation of the fertilized egg, an elevated HCG can be measured from the mother’s blood, which will prove that pregnancy has occurred. However, the concentration of HCG in the urine is affected by the concentration of HCG in the blood, so it is easy to have a false negative, so the most accurate way is to take a blood test for HCG.