am confused in pregnancy can some one explain this to me?

it's not.. Someone should be telling you your real due date

Ya it happens. I had an ultrasound with my now 4yr old that said she was past due and 10lbs. I think I was about 35wks. Then with my last baby now 9 months old that said I was 3 wks behind. At 26 wks. It all depends on if baby is laying in a way that is easy 2 measure. It can't b perfect. Plus baby can change a lot in a couple wks in the end. I wouldn't worry 2 much about it. If your dr is worried they will talk 2 u about it. I'm guess that's y u had them done so close together.

Definately not normal. You need to ring them and find out exactly when you due. I would also try and work out an estimate too from using the date of your last period so Atleast you have an idea even if the hospital don't. Good luck x