It can be a skin issue or a nerve issue. It can be a fungus, a bacteria, or some misdirected nerve impulse.
Lidocaine patches help and so do steroids such as dermatop. They stop the inflammation and the itch. Your doctor or a dermatologist can help you. Benadryl as directed can really help too or a combination of all the above.
When you scratch it, histamine is released, making you itch worse, so try to press with a cool, wet towel or ice pack if it gets going tonight. Buy some cortisone with lidocaine at the drugstore today and put it on before bed and take an antihistamine. Steroid creams or ointments available with a prescription can be a godsend and are much stronger and more effective than over the counter so call and ask for a script or sample. See your doctor and stop suffering. They may never know exactly what the issue is, but they can make it stop.
Sorry you've been enduring this so long. Sounds awful. It is treatable so go take care of it, okay?