They usually double every 2-3 days, but the actual level varies quite a bit from person to person.
2 weeks pregnant is actually about the time you ovulate, since they start counting the first day of your last period. But if you mean 4 weeks pregnant (around the time of your missed period...or 14 days past ovulation), the levels are usually a little under or over 100.
Here's a list of betas reported by women at different times in their pregnancy: http://betabase.info/showBasicChart.php?type=Single
Best of luck!
thanks so much, yes I did mean after ovulation. I was think that when I put 2 weeks