If your medication makes you feel terrible, it’s probably not the right medication. Did a regular doctor diagnose you, or a specialist? I was diagnosed by a psyhciatrist with a specialty in ADD. Unfortunately, he’s no longer available, and my GP just doesn’t have the knowledge to manage my case.
One thing that will help: Read Driven to Distraction by Hallowell & Ratey. Hallowell is one of the foremost ADD experts. The case studies they describe will show you how ADD at various ages can be managed, and their explanations (which are very readable, not overly academic) will help you understand your mind.