Can you tell me why im having pain in my leg?

Yes. You need to describe the location and nature of the pain before I can give you my opinion.
Anything. It could be coming from your skin, muscle, bone or blood vessels. It's best to see a doctor to get a more thorough history and physical exam to figure out what is wrong. Sprained muscles, pinched nerves, varicose veins, bone disorders, low vitamin d, poor circulation, dehydration, anemia and other problems can cause leg pain, among other things.
Many possibilities. When you are evaluated you will be asked where in the leg? Thigh? Lower leg? Top side or bottom? Tender to touch? What brings it on? How do you help it? Are you able to help it? Is it localized in one place? What activity does it occur with? Are there color changes? We consider a variety of causes: muscular, joint, neurologic, circulation, injury. Each can cause certain types of leg pain.