Get a percussion instructor to find out if you're doing anything habit-wise as part of your playing style that you need to change. Sometimes we develop bad habits that hinder our speed and execution in playing, and it helps to identify them and work them out of our system. I've had to go through this many years after I had stopped playing during college.
I was going to hazard a guess that you have either high salt and/or fat levels in your dietary habits, but you're barely out of high school, though... I have to watch salt and oils. I've had similar problems with my elbows in my very early 40s that stopped once I cut back the sale AND the oils (salad dressings, cooking oils, you name it). In fact, the oils were even worse than salt!
Good luck, and write up what you find out!