I’m a little confused..

So in the beginning of my pregnancy, they gave me a due date of March 2 and then I had a scan for my 20 weeks where they measured my baby and my due date changed to March 4. Today I went to a place where they do 3D ultrasounds and the lady measured her there and she said my due date was February 27. She aaid I was the baby was measuring 24 weeks and 6 days and I thought today I would be be 24 weeks exactly. She said that due dates change all the time but now I’m confused as to what my actual due date is! Has this happened to anyone?