Low beta hcg and progesterone.

Missed my period on Tuesday ( 11/5) tested positive for pregnancy, called my doctor and had my beta hcg blood test yesterday and was just called and that it was very low, reflecting a 1 week old pregnancy when I should be about 4 weeks.... My number and was 45 ... I go back tomorrow for a follow up blood test to see if it doubles... My first pregnancy I had low progesterone so I went on the pills ASAP and had a healthy pregnancy, I will start the progesterone today... Of course I'm freaking out as if I get my blood drawn tomorrow I won't here from the Dr till Tuesday because of holiday Monday.. so I don't want to be stressed all weekend!

Has any one had low beta hcg numbers and ended up with a healthy pregnancy?