Baby measuring 2 days ahead

JJ

And now I’m totally in my head thinking baby is going to be massive 😂 help! I had my anatomy scan today I should be exactly 19 weeks (but actually based on when we had sex and I think I ovulated I feel like I should be more like 18 and 5) anyone else measured ahead and not had a massive baby?? My 2 year old always measured a bit behind.