I knew I we were having twins from the earliest visit.. but that's another story. But I was showing way faster with my youngest daughter and even faster with this pregnancy And DH is soo paranoid about having another set of twins that I generally ask them to check for my first visit with the ultrasound.
I can say that carrying twins I was sick allllll the time, much more so than with singleton pregnancies.
But at this point, there's not much you can do about it, so I'd try hard not to get yourself too worried.
mom to 4 little lions (7, 7, 5, 3)