What Causes Stiffness And Intense Muscle Pain In Lower Part Of The Body?

I have been experiencing intense muscle pain in my lower body for months, especially my legs. I can press on the muscle and it hurts as if it is swollen. At night I have difficulty sleeping because of the pain. Nothing hurts on my upper body only below the waist. My joints are stiff not only in the morning after sleeping but often. Could this be a deficiency?