Smooth, round and moveable are all good signs that it's more likely to be something other than cancer.

GP's almost always refer to breast clinic just to be sure.

Hopefully, it will be a one stop clinic where you are seen and have an ultrasound on the same day, in my area they won't do a mammogram in under 40 year olds. 

Try not to poke n prod, I know it's so difficult to leave it alone but it will play tricks with your mind.

I wish you well x