You can consult another psychologist or a neuropsychologist for clarification of diagnosis. Reading, writing and comprehension difficulties often accompany ADD as ADD interferes with learning of skills esp those that demand prolonged attention or concentration. Comorbidity in these conditions is not uncommon. One will be able to give you a clear picture only after obtaining your complete history.
Next Steps
You can get assessed for Learning difficulties as well and seek skills training accordingly. You may need to also consult a speech language therapist. They can assist you with most language related problems. Medical management is usually not the first line of treatment in the absence of any physiological causes. If you have any history of head injury, neuropathy of the brain, or seizures, a neurology consult might be helpful, in which case medicines might be advised.