Do your circles come out like this?

20151226_195909.jpg

If so the problem I was having was the Y motor belt was loose.
Not the belts on the left or right for the Y axis, but the short belt connected to the motor at the back of the printer.
Loosen the screws holding the motor and push it down, but not too hard, and tighten the screws back up.
This will tighten the belt.

I would so this before trying to change steps/mm