Hidden twin 👶🏻?

Hey loves, I had my first ultrasound I measured 7weeks6days. When the tech was scanning around she saw a clear baby and heartbeat but as she kept moving around right under the baby was something beating at the exact same time as the baby’s heartbeat. She wasn’t sure as to what it was so she asked another tech for their opinion and they weren’t sure either. She didn’t think it was another baby as it looked longer, but she wants to wait for more development and check it out then, anyone had a similar experience? Or opinions on this ultrasound do you think it’s one or two?