It is possible to have a positive blood test for pregnancy but not show any signs or symptoms. This can happen in rare cases known as a "chemical pregnancy" where the fertilized egg implants in the uterus but does not develop further. Another possibility is an ectopic pregnancy where the fertilized egg implants outside the uterus. In both cases, a scan may not show any signs of pregnancy. It is recommended to consult with your healthcare provider for further evaluation and clarification. They may suggest repeating the blood test or performing additional tests such as an ultrasound to determine if you are indeed pregnant and ensure your health and well-being.