HORRIBLE pains in my calf muscles and feet....?

Ok so, under my kneecap in the back of my leg area, i feel this TERRIBLE pain, it feels like its being pushed and pulled, and after it starts to go away, its VERY sore, sometimes i cant walk because it hurts so much as to flexing my ankle, these normally happen at night, i just wake up at random and these pains occur.. + it also happens in my foot... the inner part that is. help? whats going on? can i prevent this? is there something wrong with my body? nobody i have met has had the same problem