Accessing Game Center

I'm hoping someone can help me. I was playing a few games on ipad under my old Game center id and email however when I started playing on the ipod touch, i was forced to change my game center Id and apple id because I kept receiving the accept terms notification so i now can not access any of my games under the new game center id and loss all of my progress. When I try to change my id in game center to the old one, it says its tied to another account so I know the account isnt deleted. My question is- how can i access that old account and saved progress or is it possible to transfer all the games and progress from the old game center to the new Id? I've put a lot of money into these games and collected a LOT of rare and limited creatures as well. Really hate to start over. Please help!!