Conception confusion?

[Riviera16]

Hi all,

The first day of my LMP was 16/04 so I should be 6w+5 days however when I went for an early transvaginal ultrasound yesterday they said I was 5w + 3 days however I’m quite sure that I did roughly ovulate around the 30/04 so I’m a bit confused?
The gestational sac was 10mm and embryo was 3.59mm so is that why they have put me 10 days behind as it’s measuring small? I was luckily enough to hear a heartbeat which I didn’t think was possible until at least six weeks?
This is my first pregnancy so all is new to me, any words of wisdom would be much appreciated 😊
thanks

Not sure if it helps, but my baby always measured small and was then dated a week or so behind too, I was also adamant that the dates were wrong as I literally had sex once in that cycle, so could tell you the hour of conception 😅

My daughter arrived early on their records, but bang on time based on mine.

I just had a small baby, who now is a small preschooler and my husband and I are quite petite too.

Thank you @BeeYellowMumma that’s funny as my fiancé and I are both tall so I’m surprised the little bean is measuring small 🤣 hopefully all will be okay!