baby measuring what he should, but I'm measuring 2 weeks ahead 😳

Exactly what the title reads. Just wondering if anyone else has measured so far ahead. I'm currently 18 weeks 3 days and our baby is measuring exactly that, but when I got measured the fundal height measured 2 weeks ahead at 20 weeks instead of 18. Anyone else have a similar experience and know what the even means? I always measured correctly with our daughter, so I'm not too sure what any of that means. Thanks for any advice or knowledge on the issue!