Hi Jo jo - when they tell you you are 5 weeks pg, they count from the 1st day of your last period. So, although you conceived 3 weeks ago they say you are 5 weeks pg.
Hang in there, you won't know anything until your second blood test to see if your HcG levels are climbing as they should be. I had the same issue and asked to be tested the second time only 24 hours later. They were not looking to see a doubling in my numbers (that takes 2-3 days) but just to see if the number was rising. Maybe you can call and tell them you want a second test sooner?
Good luck and let us know!
Mom to Kyle, 12
EDD March 15
****sticky baby dust wishes****