How do you kow you miscarried? Did you have bleeding and cramping? Did they take a sonogram? Your levels shouldn't be doubling if you've had a true m/c from what I know. Did they check to make sure that it's not ectopic? Hmmmmm...
I was bleeding, went to my ob and he sent me to the hospital b/c of the bleeding. they did do an u/s and did not see anything I would have been about 5 weeks at the time...
I'll keep my fingers crossed it is possible (I hear) to see nothing at 5 weeks and still be PG. and most people I know have had bleeding at some point. good luck. Keep us posted.