Dry hair, dry scalp, constipation, feeling depressed etc can be signs of low
thyroid function. Low testosterone
is another possibility. Other causes
could be anemia and diabetes.
Apart from this adolescents of your age need a drive or motivation in life. You must hae a goal (professional, personal, social etc) and work towards it. Join an activity class that can de-stress you (yoga, music, dance, gym etc). Simple walking, cycling, swimming too helps.