What is the exact location of itch?
Have you taken any medications for the itch?
What is your blood pressure & blood sugar level?
What is your height & weight?
Most likely such long itching could be due to neurodermatitis but itching can also be aggravated by long term medication also.
You are advised Platelet examination & Complete blood counts to rule out any purpura.
You can take Librium 10mg At night time which will reduce anxiety & reduce your symptoms.
Hope this helps.