Abnormal US

So I just had my first OB appointment today and thought I was 7 weeks and 6 days pregnant. LMP was January 5th. Baby is only measuring 6 weeks and 1 day. I had a positive pregnancy test on February 8th (which concerns me). We are checking hcg levels to determine if I should be closer to 8 weeks and the baby isn’t growing like it should. Has this happened to anyone else? I’m freaking out and already thinking the worst. Was so excited for today. 😢