5 week ultrasound... possible twins????

Cass
I had my first ultrasound, and it turns out I was earlier than we thought (measured 5 weeks 1 day). Tech could see one clear gestational sac, and then next to it a second, slightly smaller sac. She said this could be a twin or it could just be a water sac. We go back in one week. I've also had extra blood draws, and my numbers are rising well but doubling faster than 48 hours (at a rate 27 and then 32 hours). I know I really just have to wait my next ultrasound, but am wondering if anyone else has had similar experiences and how it turned out?