As Azland says, wait till you get your AS results first otherwise the mental stress and worries will eat you alive and make you crumble away during your exams by not being able to concentrate. And you do sound stressed.... so at least get your AS exams done before you start making options and a plan(s). Good luck.
P.S. Unless the requirements are for a specific no. of A*s, then generally, universities won't care. All that matters are your predicted A2 grades.