After streaching your ear to a 0 gauge can it go back?

It depends on the person.

Some peoples will go back to a small size, just take them out and see.

Wait about 3 months, if they aren't to a desires smaller size, you can try putting a fairly larger taper in your ear that will irritate your ear over night, then take it out in the morning, and it should shrink to smaller than before. Repeat the process if necessary.