When you drink a cup of coffee it removes two glasses of water from your system (hence, it makes you need to pee not long after drinking). I'd say the headaches, mood swings and exhaustion are from dehydration and probably the addiction too. Do you eat breakfast in the mornings? If you don't, you should as it will start your metabolism for the day rather than just relying on coffee. Limit the coffee to two cups a day - one in the morning and one at night. At school bring a drink bottle of water around with you and whenever you crave the coffee, take a sip of water.
I try not to have any more than 2 because I don't think it's good to have that much caffine all the time.
You probably are addicted, if it's giving you headaches not having it and changes your mood, then yeah. I don't know any advice to give you to be able to stop though, sorry.
Limit the coffee to two cups a day - one in the morning and one at night. At school bring a drink bottle of water around with you and whenever you crave the coffee, take a sip of water.