Hello, This is called Plagiocephaly. This problem is usually solved by itself in early infancy, as a part of normal growth along with assisted positioning of the baby during his or her sleep. If not resolved then some treatment like 'orthosis' can be done in tender ages. I am very sorry to say but as you are 17 years old, it is almost impossible to get back that previous shape. Anyway I will recommend you to visit a plastic & reconstructive surgery specialist for a further  elaborated and detailed guideline. Thank you.

Hello. Shape of head is possible to change in infancy.but as the child grows there is fusion of bones of head like that of body. Then after it can't be changed. It get a definite shape. Thanks