Pain where body meets leg?

So all of last summer, I noticed that sometimes the area where my body meets my leg...my left leg..right around that big bone ( cant think of the name right now. Is it the femur??) really hurt. I would be sitting and all of the sudden it was like I had a terrible pinched nerve. Once, I was on the back of my dad's motorcycle and suddenly that area just started throbbing. I tried to stretch my leg but couldnt. I ended up having to get off for a second. Then, one night after a sleepover, I came home and that area just killed me so bad. It hurt to walk so I walked very awkwardly. For about 4 days, I had to gimp around. Heating pads and ice packs did not work. Then suddenly it went away. It happened on and off rarely since then. Now, the other day I was on my horse and suddenly I felt that feeling again. I tried to stretch it around and it would fade and then come back whenever I moved my leg. This morning I woke up and that area is sore. What could it be? I used to have the abilty to move my leg around in it's socket so maybe that has something to do with it? I am 15 and generally very healthy.