I have been on Effexor for 8 years and am currently tapering off the medication. I thankfully did NOT experience the kind of symptoms you describe when I began. Honestly I don't think of Effexor as the "drug of choice" for anxiety disorders - isn't Paxil more often prescribed for this problem? I was prescribed Effexor for depression, and it did work for me for many years - until after 3 years when I became chronically fatigued (which I blame on the drug). Perhaps because you are having such severe initial side effects, it is not the appropriate drug for your condition. I would get a second opinion (or third actually!) if I were you. Try to find a doctor that doesn't give these pills out like aspirin (and I hope that you never do!).
But all in all I don't recommend ADs for long-term use. The clinical trials are conducted for 12 months only - so long-term effects haven't been documented. Also, I would try every other form of therapy before medication - I agree with wannabehotguy that you should try cognitive behaviour therapy, which is supposed to work wonders for panic disorders. I think that especially since you are beginning what is quite a stressful career, you should get to the bottom of the cause of your anxiety.
Wish you all the best!