Hi Rondo, perhaps you need to talk to your parents & they can take you in to see your dr to have things checked out. The dr should be able to help out by giving you some exercises to help with your posture.
Your book bag should not be heavy as that will affect your posture & can cause unwanted issues. If I remember correctly a book bag should not weigh more than 10% of your body weight. I have a 12 yr old grandson who is small. One thing his parents do is to make sure the bag is not too heavy.
Moderator in Chronic Pain & Psoriasis Forums