Day at the ER/ confusion!

I spent the majority of my day yesterday at the ER checking for a blood clot in my leg. I don't have one, thank God, but they couldn't check my nerves to see what's going on because those test are harmful to baby. While I was there my OB called saying my progesterone is low. Being a small town everyone knows everyone, the ER doc is a family friend so he got me an ultrasound of baby. Well, according to my very first ultrasound I should've been 9w4d, according to my second I should've measured 10w2d (I should've measles that yesterday) well I actually measures 11w2d so how freaking far along am I? Baby is either growing like the hulk or I'm more pregnant than I thought. Which we really don't know how far along I am considering I don't know when my last period was.