Confused! 10 or 14 weeks??

I went in for my first ultrasound thinking I was 10 weeks according to my cycle. Doctor said I was off by a month and I’m actually 14 weeks. Baby and heart rate all look good. And guess that explains why I’m showing...

We were actively TTC so I’m 100% sure of my cycles and the date that I got a positive test so i was pretty shocked when she said 14 weeks. I always had a normal, 5 day period until i got my positive. Im confused and a little freaked out. Anyone had this happen?