Freedom,
That could be some of the reasons. Pressures of a new school, puberty, hormones, can all factor into the equation. Talk to your doctor and in the meantime do some relaxation techniques. Read a book, go for a jog, take a hot bath, go to the gym. Take whatever relaxes you and do it when you wake up in the morning, so you have a fresh outlook on the day. Also, do your relaxtion before bed. This will calm you down from your day's activities.
Try your doctor as well as see what is suggested.
Keep us informed, we are here to help.
Josie