So i dont believe my tile was sealed before it was installed. it has changed color a little bit and has lost its shine. How can i get it back shinny?

If a polished tile has lost it's shine, it sounds like it has been etched. Acids in cleaners such as vinegar can etch polished stone. Contact a stone refinisher in your area, as the only way it can be repaired is to be re-polished. Be sure to use only cleaners that are made for polished natural stone and seal your stone using a penetrating / impregnating water based sealer.