im 15 and male..

i have had an achy pain in my right forearm for a couple of years, if i lean on it for a couple of seconds or minutes it feels like i have stopped the blood and begins to ache, my other arm doesn't do this. And if i hold my arm in a certain position or whatever it starts to have this aching sensation. the pain is on/off and i am curious to know what it is.. there are periods of time when it doesn't bother me and sometimes i go through a patch where it hurts alot and annoys me. Last night it woke me up.. please could someone give me some suggestions of what it could be?