To me it sounds like you have little major prep for any of the majors you were originally interested in and it sounds like you might end up staying longer than 2 years regardless of which major you choose at this point. I would sit down with your academic advisor and try to map out a strategy and hopefully they have suggestions on what would be the best path to take. Have you gone to your orientation? I would see if you can talk to some one UCSD now and try to figure things out.