I have some red bump in the middle of my head for more than three months, i used medicated shampoo and other things and it not working. i don't k?

A picture is worth..: ..a thousand words. There are NUMEROUS causes of a red skin bump. Perhaps most likely is a small hemangioma/blood vessel proliferation or tiny blood vessel injury. Other possibilities: an infected pimple, eczema/dry skin, contact allergy (touching something irritating). Submit a picture to HealthTap or see your Doctor/Dermatologist for diagnosis; 3 months is long enough to wonder:)