Is it normal to measure behind then ahead then behind a little again?

When we first had an ultrasound baby measured three days behind based on my LMP (didn’t know when I actually ovulated) then she measured ahead two days at the 11w ultrasound and at my 14 week she’s measuring behind two days again lol is that normal for measurements to go up and down like that? She was also pretty scrunched up at this one lol