A line 20 days after intercourse is usually an indication that there is no pregnancy. However, there may be false negatives, due to incorrect testing methods, expired test strips, or the level of HCG value in the early stages of pregnancy is not high enough to show, so you can test again with morning urine after a week, or you can go to the hospital to check the concentration of blood HCG, the results are more accurate. Pregnancy test paper determines whether you are pregnant by detecting the concentration of human chorionic gonadotropin in your urine. Generally, within 3 days of intercourse, both sperm and egg may combine. 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 the 10th day, and in urine after the 12th-14th day. Therefore, it is recommended to monitor continuously, using the middle part of the morning urine to observe dynamically; you can also go to the hospital to test the blood HCG value, which is the most accurate. If you are not sure, you can go to the hospital to draw blood to test the value of human chorionic gonadotropin, if it does not exceed 5mIU/ml, you can rule out the condition of pregnancy. You can increase the possibility of pregnancy through the following ways: 1, light diet: avoid eating greasy, 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 body’s intake of vitamins and dietary fiber; 2, to ensure that sleep: you should develop a good work and rest habits, to avoid staying up late to ensure that rest, so that the body is in a good state; 3, the amount of exercise : can be appropriate aerobic exercise, such as slow walking, yoga, etc., to promote the body’s metabolism, improve the body’s physical fitness; 4, relaxation: relaxed, happy mood also helps to conceive, you can participate in more activities, keep upward mood.