Our heads are heavy! its our neck muscles' job to support it &they can get sore from holding your head in a position all day.
Ex. Studying, working over head, sleeping in an odd position. Osteopathic doctors (D.O.) can do treatments to help realign your neck (& rest of your body) & muscles. You may be holding your neck in a certain position to compensate for a misalignment elsewhere. See your dr.