I would recommend that you go to see your primary care doctor
about this issue. It sounds like it has been going on for quite a while, and any persistent skin condition should be evaluated by a doctor to help figure out whether or not it needs treatment.
By far the most common cause of a persistently itching scalp is something called seborrheic dermatitis. This is a chronic condition of the scalp which causes itching and flaking. Mild cases of seborrheic dermatitis are commonly known as 'dandruff'. Your doctor can take a quick look at your scalp and help figure out whether you are showing any signs of seborrheic dermatitis. While doing so, they can also rule out other common causes of scalp itching, such as eczema
If this does turn out to be seborrheic dermatitis, then simple cases can often be treated with just a dandruff shampoo, of which there are many different brands available in any supermarket or drug store. On the other hand, more severe cases might require a prescription strength lotion or shampoo. Your doctor can help you figure out what treatments you should start with, and they can also follow along to make sure things are getting better!