My cat is being very clingy all of a sudden?

It all depends on if it is an inside cat or outside cat, if you let your cat go outside, then it may have run into a raccoon or something that scared it or maybe, someone in your family who your cat used to be attached to has been ignoring her/him...your cat could just be trying to get attention, my cat gets extremely clingy and acts cute when she wants food, and now she is as big as a house! I don't think that your cat would be going through her/his teenage stage because your cat would be over 28 years old!!!