It can be detected 2-3 weeks after intercourse. You can use early pregnancy test paper or pregnancy test stick to collect morning urine for testing, which is more accurate. If you are not sure, you can go to the hospital to collect venous blood for testing. The main thing is that it is possible to get pregnant if you have sex without contraception, but the chances of pregnancy are different, the chances of pregnancy are higher during ovulation, mainly because the combination of sperm and egg will be pregnant, if pregnancy is determined after testing with the test paper, you should also go to the hospital for a formal examination, the testing method is not the final determination of pregnancy. You should do a pre-conception checkup when preparing for pregnancy to ensure your health before you get pregnant. You must take folic acid supplements in time during the early stages of pregnancy to prevent fetal malformations, and you must not have intercourse during the early stages of pregnancy, otherwise it will easily cause fetal miscarriage.