you would own the copyright in the material you created. That gives you the right to reproduce your stories wherever you wanted.
The other site. We don't know what your arrangement was with the other site but you may have created an implied license based on your behavior. That is, the fact that you posted at the other site, implies you granted them a right to display the material. If there is no implied license (and no evidence granting rights to the other side), you can ask to have your copyrighted materials removed.