I have had severe leg pain in the back of my right leg that continues to go down to the back of my knee. When I sit or lay down, it is a lot worse. Once my leg has relaxed the pain is so severe. I can walk around and the pain is not so bad but, it still hurts. If I lift my leg it hurts but when my leg is laid back down, it again starts hurting severely. What could be the problem? It has been going on for at least 1 month and as each day passes the pain worsens.