While it is sometimes used off label for treatment of ADHD, Wellbutrin is not approved for that purpose and I'm not familiar with any studies where it had any conclusive effects. Wellbutrin is primarily an antidepressant, though it acts on different neurotransmitters than does your Cymbalta, and there has been anecdotal evidence of it helping with ADHD.

ADHD meds generally come in one of two different types. Stimulant meds, such as Ritalin (Methylphenidate), Adderall (various amphetamine salts), Dexadrine (Dextroamphetamine) and others act by causing the underactive parts of the ADHD brain to be stimulated, and release more of the neurotransmitters that we are short on. Stimulants start to act pretty much immediately, but have a very short lived effect. Many stimulant meds are prescribed in time release formulations in an attempt to extend their effects.

Antidepressant style meds, such as Wellbutrin and Strattera attempt to make up for the understimulation of our brains by preventing the reuptake (breaking down and reabsorbing) of those neurotransmitters that we don't produce enough of. They tend to take as much as a month or six weeks to reach full effect, and the effect takes time to fade when the medication is stopped. The biggest issue with antidepressant style meds is that they don't always target the right neurotransmitters.

Ultimately, different meds affect different people in different ways, so finding the right medication or combination of medications is generally done on a trial and error basis. Take your time and do your research, in the long run, finding the right meds at the right doses will make all the difference.