my last sonogram said I was 7 weeks but that doesn't match my last period. ..can that happen ?

Yes, you could have ovulated later, or earlier.

true. Ok thank u

Plus you're not actually pregnant at your last period. So like with my last period I would've been 6 weeks and 6 days at my ultrasound, but I was only 6 weeks and 1 day according to measurements.

But the actual fetal age was only 4 weeks 1 day

Or something like that. Go by what the ultrasound said, not by when your last period was. Although if it only differs by a few days it doesn't really matter

Go off of the due date they give you. My baby is measuring at 31 weeks but my due date places me at 28 weeks. I asked my midwife if his size changes my due date and she told me no. That babies go through growth spurts and sometimes the measure differently than what's considered "normal" for their gestational age. She told me I should still go off of my original due date given by my doctor no matter how big or small he is.