very concerned about HCG levels

Hi,

I have a history of miscarriage so I am worried. My last period was
July 24th and I ovulate on CD 12. No period came, so I took some
HPT's. The early brands (can test 4 days sooner) say positive.
Regular brands say negative. OB did a blood test on 28 days past LMP
the HCG level was 56. This is really low, correct? If I ovulated on
day 12, then my HCG level was a 56 at 16 days past ovulation. I'm
afraid I'm going to lose this one too. Did anyone else have a low HCG
level this early? They plan to do another blood test, but in the
meantime I am worried. I also have no sore breasts, no nausea. I did
have those things at this stage with my daughter.

Thanks.