HI Its called Dysmenorrhoea in medical term.its normal condition. Many girls wil have such problem in that age.You Can take Medicine like T Meftal spas two times/three times in day during periods days. It will definately improve your symptoms.If you have still very severe pain than please do ULtrasonography of pelvis to rule out any endometriosis . But 80-90% in such case like yours its physilogical so nothing to worry, Be relax Thanks