Not as far as I thought

Been to the hospital today for a dating scan and to see if baby's ok, and it turns out that I'm not as far gone as I thought I was, tracking back to when my last period started I thought I was around 10 weeks by now but apparently I'm only 6 weeks...! And aparantly thats normal for diabetic mums to feel further along than they're meant to be. Don't know why that's annoyed/upset me so much? I mainly wanted to know if baby was ok and thankfully all seems fine :)