Just a word of warning here. I know from experience that you can get very misleading results from regular HCG checks. My results had me and the doctors convinced that I was going to lose my, baby but I didn't.
My levels were at the lower limit of the expected range and were taking 5 days to double instead of 2. Most docs would agree that that is not a good sign. However, I've since spoken to a specialist who has said that the information most docs were taught is outdated and simply not accurate. Every pg is different and u/s is the only way to really know what is going on.