I'm excercising for 4 days and i also did the 7mimute workout and now i feel pain in my leg when i exercise. what can be the reason? lack of calcium?

Get checked by Dr.: For someone as young as you, you should not have any reason to have pain when exercising unless you have injured yourself and/or there is an underlying condition. In particular, if you are having increased pain with activity, you may need to have circulation checked for a condition called claudication. I would recommend you see your doctor and be properly examined. You don't want to delay this.