Stabbing pain in right leg?

Ok for about 5 years now I have experienced a horrible pain in my right leg. It feels like someone is stabbing me with a metal rod or something along those lines. It hurts midway up the outside of my thigh and right below the left side of my knee. As if a rod was being inserted in my thigh and exiting below my knee(or vice versa). It doesn't happen often(maybe 3-4 times a year) but lately it has been happening for the last three nights(couple times a night). I have no idea what it could be and there is nothing I can do to stop it. Just have to let it run its course. It is so painful that it brings me to tears and doubled over. Each time it happens its almost like the pain pulses(it will hurt for 2-3 seconds, then stop, the start again, for about 3 minutes.) If anyone has any ideas I would love to hear them. Thanks in advance for any input.