Uterus measuring big?


So I went to my 8 week check up. The mid wife said my uterus was measuring 14 weeks?? But I know I’m only 8 weeks 2 days at the time. My period is every 28 days. I’ve been going to a fertility doctor I was checked for fibroids and did not have them 2 years ago. Has anyone had this happen? This is my 5th pregnancy and fourth baby. So I was thinking maybe my uterus is just stretched out? I don’t want to worry, but I’ve never heard of this before