Is this normal

So literally everytime I go to the doctor he changes my due date! At first it was March, then he changed it to February, then he changed it to January and then back to February. I know this happens to a lot of women but why so much and by so many weeks? It's not like a few days it's like he changes it by a whole 4-5weeks! I've also seen different doctors and they're like you're ONLY 16 weeks? And everytime I go to the doctor they tell me my daughters measuring way ahead. My nurse says she thought I was 22-23 weeks 😐😐