If you are taking a total of 400mg per day of wellbutrin and 120mg per day of cymbalta, these are antidepressants, that are used to treat depression and anxiety. How are you being treated for rheumatoid arthritis? Are you taking any other medications.
You need to visit your GP for a physical and bloodwork. Although frequent tiredness can be a symptom of depression, there may be something else going on with you. Talk to the doctor about checking your thyroid levels, as they may be low. Have your blood pressure checked to make sure it is not too low. The doctor will do a complete blood count to see if you are anemic and need to take supplements. In the meantime, eat a diet that is rich in vegetables and fruit. Drink plenty of water. Talk to your doctor about doing a medication review and adjustment. You may feel need a change in dosage. I see that you have already tried other antidepressants, but it can take time to find the correct combination for you.