Telling off your doctor is not particularly helpful to solving your problem.

I'm not a medical doctor, but I have a bunch of friends who are. They tell me that the world of psycho-active medications has changed radically in the past few years. Newer drugs have fewer side effects and presumably work better than the old ones. Your best bet (assuming you could afford it) would probably be working with a good psychiatrist, that is, a shrink who can prescribe drugs. For all I know, there may be exercises or other forms of training you can do to help with your focus issues, particularly in combination with the right drug regimen.

Medicinal herbs, on the other hand, are effectively unregulated (they're treated as "food supplements", not "drugs", so they're not held to the same standards). Potency can vary from one bottle to the next and from one brand to the other. For whatever else you dislike about the drug industry, at least their products have well-understood effects on the body.

If you're insistent on self-medicating, you would do well to start off with other things besides medicinal herbs. Try tweaking your sleep schedule. Try increasing your athletic activity. Try changing the carbo/protein balance (or the real food / junk food balance) in your diet. All of these things can change your mental state; a healthy mind needs a healthy body, after all. Whether or not such changes will help you is a long-term question that you can answer through self-experimentation. Neither herbs nor any other thing you can change will be a short-term fix to help you with your accounting test. Psycho-active drugs (at least, the non-recreational varieties) don't kick in immediately.

(Obligatory side story: I had some kind of bacterial infection a few years ago, and they gave me one of these new high-tech antibiotics. One night, I got seriously hyper: elevated heart rate, the works, and for no apparent reason. I went to the drug's web site and read the full doctor's information brief on it. Sure 'nuff, it was listed as a rare side-effect of the drug. Try doing that for yee olde herbal remedy.)