If your pregnancy test at 18dpo shows two dark lines, it is typically a positive result indicating that you are pregnant. The presence of two dark lines indicates that the test has detected the hormone hCG (human chorionic gonadotropin) in your urine, which is produced during pregnancy. It is important to note that false positives are rare, so it is likely that you are indeed pregnant. However, it is always recommended to confirm with a healthcare professional and schedule prenatal care to ensure a healthy pregnancy.