The fact that you are already pregnant and can’t detect the pregnancy test may be caused by the short duration of pregnancy, incorrect use of the test, dilution of urine, etc. The test can also be used to detect the presence of HCG in the urine. 1. Short pregnancy time: already pregnant but using a pregnancy test can not detect pregnancy is likely to be due to the short duration of pregnancy, the HCG content in the urine has not been significantly increased resulting in the pregnancy test can not be detected. You can reuse the pregnancy test a few days later, and the result will usually be positive. 2. Incorrect use: Using the pregnancy test in an incorrect way or using an expired or damp pregnancy test may lead to false negative results. It is generally recommended to follow the instructions to use the pregnancy test stick to measure the morning urine, the results are more accurate. 3. Diluted urine: Drinking a lot of water before using a pregnancy test results in diluted urine, which may also result in a false-negative test result, and the pregnancy cannot be detected. The pregnancy test is only a preliminary method of determining pregnancy, and should be combined with blood HCG to confirm pregnancy.