Where exactly are you having the majority of your pain symptoms? Are you under any stress at home or at school? When was your last physical? Do you have any chronic problems?
I am sorry to hear that you have been experiencing these random pains with different degrees of severity.
Pains can happen when there is damage due to a excessive exercise and especially if you do not do warm ups first. I presume that you do take part in some types of physical exercise and/or sports at school and I hope that your teacher gets the class to do warm ups before you use equipment or sport activities.
Damage can happen in the bones, muscles or tendons. When we get a cold virus or other viral or bacterial infection that can also cause random pains in the body.
Muscles and tendons can cause pain if these are overused or not properly warmed up before you do sports.
It is not uncommon for children to get arthritic problems. If you have been experiencing these problems on and off for over 2 weeks now, I suggest that you get a parent to make an appointment for you to be examined by your doctor.
Make sure that you have a healthy and well balanced diet with lots of fluids (keep off or cut down on juices and pop). You can drink some fruit juice, but you should also drink water and milk or yogurt drinks. You may think that you have stopped growing, but your body (even when you become an adult) requires calcium and Vitamin D for healthy bones and teeth. You can get calcium from dairy foods - milk, cheese, yogurt. Vitamin D is in egg yolks, butter, fish, certain mushrooms and also your body can make Vitamin D with exposure to sun (not too much sun, you don't want to get sun burn or sunstroke). Cereals are also fortified with Vitamin D.
If you have a wide and varied diet you will not need any vitamin supplements. If you are a fussy eater and do not eat very well, you can purchase multi vitamins specifically for your age group.
Before you see your doctor, write down a list of where you get the pains, how long they last and how painful they are. You may use a numbering system to explain your pain levels, eg. 1 being the lowest pain and 10 being the severe intolerable pain. Keep a diary and write down where the pain is, how long it lasted and so on.
If you do get menstrual cycles, see if the pains that you get come around a week or so before your periods start as there may be a link to your monthly cycle.
The doctor may decide to send you for imaging tests and/or arrange a blood test to see if you have an inflammatory disorder like rheumatoid arthritis.
Hope you get on OK,
Let me know how you get on.