can i make my ex pay for bills he used even if the credit cards are under my name?

Yes, depending on the circumstances.  The issuance of a credit card in your name reflects a contract between you and the credit card company; it doesn't affect your separate arrangement with your ex.  Thus, for example, if you allowed him to use the card with the understanding that he would pay for what he charged, you can recover from him; if you allowed him to use the card as a gift, you can't recover.  Either way, however, you are still responsible to the credit card company, whether your ex pays you back or not.  The only way you would not be responsible to pay the credit card company would be if you did not authorize your ex to use your card, but even then you could have a problem if you put your ex in a position where he could misappropriate the card.