If your urine pregnancy test is positive but the ultrasound shows no gestational sac at 5 weeks and 5 days, it may indicate a possible early pregnancy loss or an ectopic pregnancy. It's important to follow up with your healthcare provider for further evaluation and monitoring. They may recommend additional tests such as blood work or repeat ultrasounds to determine the cause of the discrepancy. In some cases, it could be too early to detect the gestational sac on ultrasound, so your doctor may advise waiting a few more weeks for another scan. Remember that every pregnancy is unique, and individual circumstances can vary. Your healthcare provider will guide you through the necessary steps based on your specific situation.