Possible twins?

We went for our ultrasound at 5 weeks. I had an ectopic last pregnancy so they wanted to make sure everything was where it was suppose to be this go around! The ultrasound tech saw two sacs but one heartbeat. The thought of twins scared me to death at first but now I can't imagine not having them!!! We go back in two weeks for a follow up. This will be the longest two weeks ever. Did anyone else have something similar happen to them? Did it end up being twins?