Amphetamines often create or exacerbate compulsions which can become behaviors so ingrained in us that they are incredibly difficult to kick. The hair pulling disorder you are thinking of is called Trichotillomania. Skin picking and Trich are very similar in nature, thus treatment is basically the same.

Depending on the severity, behavioral therapy along with medication has been the most successful approach, but the disorder is generally new and not well researched. Success is rather limited, but many people have gained great relief. Talk to your doctor about it as soon as you can, before you do any more damage to your scalp!