A line measured 20 days after intercourse is usually an indication that there is no pregnancy. However, it may be a false negative due to incorrect testing method, expired test paper, or the level of HCG value in early pregnancy is not high enough to show yet, so you can test again with morning urine after a week, or you can check the blood HCG concentration at the hospital for more accurate results. A pregnancy test determines whether you are pregnant by detecting the concentration of human chorionic gonadotropin in the urine. Generally, within 3 days of intercourse, both sperm and egg may unite. 6 days after the formation of a fertilized egg, placental trophoblast cells begin to secrete a small amount of this hormone, which can be detected in maternal serum after day 10 and in urine after day 12-14. Therefore, it is recommended to monitor continuously, using the middle segment of morning urine for dynamic observation; you can also go to the hospital to test the value of HCG in blood, which is the most accurate. If you are not sure, you can go to the hospital to have a blood test for the value of human chorionic gonadotropin, if it does not exceed 5mIU/ml, you can exclude the condition of pregnancy. You can increase the possibility of pregnancy by the following ways: 1, light diet: avoid greasy and spicy food, such as barbecue, spicy hot pot, etc. You can eat more fresh fruits and vegetables, such as oranges, celery, etc., to increase the intake of vitamins and dietary fiber in the body; 2, ensure sleep: you should develop good habits, avoid staying up late, ensure rest, so that the body is in good condition; 3, moderate exercise 3. relax: you can do aerobic exercise, such as slow walking, yoga, etc., to promote human metabolism and improve the body’s physical fitness; 4. relax: a relaxed and happy mood also helps conception, you can participate in more activities and maintain an upward mood.