Hello,
I was worried about my hCG levels and found this article to be very informative. I hope it helps!
http://blogs.webmd.com/healthy-pregnancy/2005/11/hcg-levels-and-ultrasounds-in-early_30.html
I have been going through the same thing since 3/03/08. My hcg levels are also low and slow rising, and I am 100% sure of the date of my LMP (2/06/08). I have been told that I might have ovulated late in my cycle, etc., etc. Every other time I go for a blood test or ultrasound, I get a different story.
One thing that I have learned from medhelp: Don't make too much of hcg numbers!
I think we'll both just have to wait and see what happens week by week! Waiting is the hardest part right now, and not knowing the outcome is agonizing! I certainly sympathize with you, and I wish you the best of luck!
Are you sure you are right about your dates? Maybe you ovulated later. If that is the case - then it is too early to tell. However, if your dates are wrong then those HCG levels are low. The only way to tell for sure is to repeat the ultrasound next week or so. I did experience the same thing last year and I did miscarry. I sure wish you the best of luck and I know the waiting is hard.