Can a ct scan be mistaken?

read all? I'm on clomid 150mg had 4 mature eggs on the 14th day of my cycle I started getting slight cramping and headaches around 9dpo so I was uming pregnancy well I went to the er and. they done a CT scan on me in which he said was a cyst that had fluid..its 7.5cm is there any way he could be wrong and it could be a baby? Because wouldn't my reg doctor at the Obgyn have seen the cyst when he checked my follicles? So I'm wondering can he have maybe mistaken a baby for a cyst? All help is greatly appreciated =] thanks in advance