see a good psychiatrist. xanax works wonders with a lot of people, especially for short term treatment. Longer term use is somewhat controversial, but it depends on the person. There are other antianxiolytics out there, all with pluses and minuses. You can also look at CBT (cognitive behavior therapy). And of course getting with a psychologist to get at the root issues is the best plan of action...but in the meantime you need to get some relief. And don't necessarily trust what your GP says. They often underprescribe.
http://www.adaa.org/AnxietyDisorderInfor/GAD.cfm