Hi Chekigal,
Did you have any HCG in your first BT? If so, or if your progesterone is still high, they often like to do repeat BT's to make sure they return to normal so that there is no trace of HCG in your system which might later suggest an ectopic OR might be a very late implantation but not likely unless they made this suggestion. They should have told you about when you rang for your intial BT results that you would need another and why you would - either way I would be ringing to ask why you need the repeat, but I suggest this is likely the reason.

Hope this isn't stressing you too much