Gestational Sac

Crystal

By dates I'm 6 weeks and 3 days and went for a confirmation US and only saw a gestational sac measuring about 6 weeks. My Hcg numbers at 4 weeks 3 days was 66, at 4 weeks 5 days was 191, and at 5 weeks 2 days was 1149. The doctor said the gestational sac looks good and she thinks I'm just not as far along as I thought based on HCg numbers and only seeing a gestational sac. Has this happened to anyone else? Did you have a positive outcome?