Early ultrasound

I went for my first ultrasound on Friday and to my surprise there were two sacs but no babies in them yet :( I'm going back this coming Wednesday for another ultrasound and my doctor said he would hope to see the babies and their heartbeats. So many different thoughts, freaked out about having another miscarriage but the possibility of having twins with the problems I have freak me out even more!! Anyone have something similar or words of encouragement are really appreciated. Baby dust to all