First pregnancy 5 weeks

I had my first ultrasound today at 5weeks. So when the doctor began the ultrasound I saw that there were two sacs. However one is smaller and she said it could be fluid but that doesn’t make sense to me why does it look like a sac. She then said twins possibly then took it back and said it nothing. Since I’m really early my doctor said it’s to soon to see anything. So far I have an empty sac. Has anyone else had an experience with this? My next u/s is June 3rd and I will be 7 weeks. I’m a little nervous she did mention of possible miscarriage can happen; however, I shouldn’t worry. Hopefully I see a little nugget next time and hear a heart beat. 🙏🏼👶🏻