I am getting severe upper leg pain.?

For the last few weeks i have been getting a severe pain in my upper right leg. its not constant, it comes about every hour or so and only lasts about 3-5 seconds. when it comes it is absolutely agony and my leg also feels kind of "dead". I cant localise an area that is painfull it feels almost in the middle of my full thigh. Its getting more frequent now and is very worrying. does anyone have the same or any clue wot could be causing this?