Tired every day, even after sleeping 8hr

Hi, i went to a GP, ordered blood tests, was vitamin d deficit, but now no deficiency after 40 days of meds. He told me i am just stressed which i don't think i am. I sleep from 12:00 PM to 9:00 AM sometimes 10, and even then i feel horrible. Its like there is a rubber band tightening my head, and i feel i am too tired to do anything, like understand games i am playing, study for more than 1.5 hr, and for comparison i used to pull all nighters 8 hrs straight, no breaks, for my boards and scored pretty good as well. I don't have a comparison chart as to if what i am feeling is severe or mild tiredness, i just don't feel good and that something is wrong and i don't know why. Please tell me if i should go in person to a neurologist clinic and that can he help me? Any useful suggestion is greatly appreciated. Thankyou.