If you can’t detect pregnancy with pregnancy test, it may be because the pregnancy days are short, the HCG level in your body is low, and the level in your urine is not as low as the level that can be detected by the pregnancy test, so the pregnancy test can’t detect the pregnancy. You can go to the hospital to have a blood test for HCG. Blood HCG is a very sensitive indicator. It can be measured 10 days after intercourse, i.e. 10 days after the formation of the fertilized egg. If there is a doubling of HCG on dynamic monitoring, the embryo is considered to be well developed. If the HCG hovers at a low value, does not double or even decreases, the embryo may be underdeveloped or ectopic.