If you truly have optic neuritis with that much pain, you should be taken care of immediately. Many patients get hospitalized and treated as an inpatient with IV medication for this condition (it would all depend on your examination and history). The diagnosis also needs to get confirmed and you may need an MRI exam as well if not done already. You should seek the opinion of a neuroophthalmologist immediately. If you live near a large university with an ophthalmology residency, you should have access to their hospital and neuroophthalmologist on staff. Most of these programs have a urgent care eye walk in clinic which would bring you to their attention if you are having trouble getting an appointment right away.
HV