I need some twin momma Input!

Raesha
So I had my dr apt today at 11 weeks 5 days. I went in for a uti and had to see a different dr since mine was not in today. She went to listen for the heartbeat and we found baby on the lower left side of my belly but then again moments later on the upper right side just a cm under my belly button. She thought it was very odd how far ahead I am measuring and suggested that I am further along. But we did an ultrasound at 6 weeks because my hormone levels were super high and my dr wanted to know how far along I really was. We saw one baby and it actually measured 4 days smaller than I had calculated from my dates. But the ultrasound tech couldn't see around baby, so she she wasn't able to see my left ovary or the entire left side of my uterus. Ultrasound lasted about 5/10 mins. 
When she measured my belly today i am measuring about 16 ish weeks. My uterus is less than a cm under my belly button. She set me up with my dr in two weeks to get rechecked and see if I have grown and if so they will go from there. I guess I just want to know if anyone else who was having twins have something similar happen? I was measuring about 1.5 inches under my belly button at 8 weeks but the nurse practitioner didn't think much of it and brushed it off. I'm just anxious now that I have to wait two weeks to hear what my dr thinks! She got me excited and nervous saying that it could be two in there. Any input would be nice :) thanks in advance!