Head never stops itching

So last year I tried a new brand of hair gel and ever since my scalp has been non stop itching. I stopped using it but a year later my scalp still itches and nothing helps. I've tried 4 kinds of scalp shampoos, 2 kinds of oils, ive tried vinegar and baking soda rinses, I've cut my hair, I've tried washing my head every 3 days to every 2 weeks and nothing has helped. If I don't wash my head atleast once a day it itches. I went to the doctor about it but she said nothing was wrong which is obviously not true. Theres no visible problem on my scalp and my hair grows normally so I'm not sure what's wrong... anyone know a solution?