5 weeks , thought I was 6.

Went to the doctor yesterday . I was thinking I was 6 weeks from the date of my LMP. I had a scan done , and she said she was measuring me about 5 weeks . There was nothing but a gestational sac to see . I have no bleeding. They scheduled me for another scan in two weeks but I can't help overthinking all of this. It was my first month off birth control so maybe i ovulated late ? This is going to be a long two weeks .