First round of blood tests...

Am
Got my first blood draw yesterday since having positive tests Friday. Beta of 41.3. 4 weeks today. Doc sounds pretty optimistic, wants my levels 60-80 next draw. Started me on progesterone 2x a day.  I'm so nervous! This is my 4th pregnancy for baby #1 and the farthest I've gone with high hcg levels. I feel like my test today took longer to get the same color I had yesterday. I'm sure I'm just making myself crazy!!! 
Anyone had levels in the 40s at 4 weeks and go on to have a healthy pregnancy?