Checking your HCG levels can be an indicator of pregnancy, but it is not the only factor to consider. A HCG level of 166mUL/ml is within the range that is typically associated with early pregnancy, but it is important to consult with a healthcare professional for an accurate diagnosis. They will consider other factors such as your symptoms and medical history to confirm whether or not you are pregnant. Additionally, it's worth noting that HCG levels can vary between individuals, so it's best to rely on a comprehensive evaluation from a healthcare provider.