I would just ask your Dr. There is conflicting evidence when it comes to twins though, some pregnancies have more or less HCG than others they don't know why it happens but sometimes it does. So they might be able to find out if you have twins this way however my SIL was told she was more than likely having twins with her first pg'y but it just turned out she just had a high HCG levels. As far as I know also your HCG levels either plateau or lower after a certain time (I think its 16 weeks, someone can verify this for me ) so you can only have your levels checked up to a certain point, but generally you wouldn't need it done after that anyway

So basically just ask your Dr. They may even be able to tell you if you have already have had a blood test as they often do HCG levels then without you even knowing (some tests only show >x or <x which either states a pos or neg).

I hope that helps! I am soooooo excited for you Nikki! I hope everything goes well and fingers crossed I won't be too far behind you It would be so great if at our next BB meet you me and anney were waddling along

*hugs*
Cailin