I hope that your bHCG is incorrect, but the test result you recieve on Monday will be more conclusive. Generally, your HCG should double every 2 days. If yours is decreasing, it can mean that the fetus may not be forming...something called a "blighted ovum". I have seen this condition go to 12-13wks and be totally asymptomatic, and when I do a routine U/S, BOOM, no baby, but all the symptoms of being preg. I had a miscarriage prior to my son, and my numbers halved every 2 days. I was bleeding though. Good Luck, and I will keep my fingers crossed for you!
Also, I should have mentioned..a tubal preg can also cause HCG not to double every 2 days either.