Told by ultrasound tech it's twins?!?! I'm confused!

Silvia • Married 4 Years. 3 Babies. Work Full Time at a Respite Agency. And Come Home to be a Wife and Mother.
I had an ultrasound done a few days ago and while she was doing my ultrasound she looked at me shocked and said she was sure I was having twins. My first two vaginal ultrasounds only showed one. I'm so confused. I won't see a doctor for another month! I'll post pics of all my ultrasounds I just want to get opinions. I've read that sometimes one baby will cover the other. I'm sure and positive it's just one but I've had two ultrasound techs assure me I have twins!