These pains seem mysterious to me. If you were 30 or older, I'd say you should read up on ergonomics and adjust your seat, desk and PC position. But your profile says you are 14, and an average 14 y.o. body can take a lot of un-ergonomic (ab)use before it starts to hurt.
That is... unless you have had an injury from sports or from an accident. That may have pushed some bones and joints in a wrong position, causing pain. (Note: It could be an injury in the shoulder region or lower down in your spine. The cause of the pain does not necessarily have to be where you feel it.) In that case, consider a visit to a doctor. Another possible explanation is that your body has had a growth spurt, making it extra sensitive to a wrong working position.
In any case, take the pains seriously. The neck is a delicate piece of machinery. If the muscles in the neck go haywire, you can get terrible headaches.