Why does my leg do this?

For the past year or so I have been having this annoying problem with my right pelvic/femur joint. If I go to open my legs for any reason sometimes it will cause this sharp stinging pain at the joint. I don't know if I am pulling a muscle or not but it causes me to double over in pain. It hurts sooo bad. It doesn't do this every time though. Also if I am laying flat and doing leg lifts I can feel something in that joint popping out of place. I don't know if this is relevant or not. Any ideas what is wrong??? Please??