Is this normal?

Chelsea • Married in May 2011. I have two babies, both born on Valentine's Day 2012 and 2016. 💜💚
I had blood tests and stuff yesterday and they called and said "congrats you're Pregnant, but we need you to come back and re run our tests next week" 
Is that something that normally happens? I'm only like 5 weeks along (according to my last menstral cycle)