Why am i so sore and tired?

Im 15 and very athletic. My knees have been constantly sore and bruised for a while but in the past few weeks my knees have had shooting pain in them just from sitting down or going up the stairs and since i have taken a brake from sports, the pains have gotten worse. and its not just my knees. its everywhere also my ankles arms head and sometimes back. i drink at least one sometimes 2 or 3 cups of milk everyday, too. and recently i have been very tired. I have been laying in bed by ten every night the past few weeks and haven't been able to fall asleep till about one AM. then i wake up around 8 and cant fall back asleep. i have just kinda been tired overall lately. even with being out of soccer for a few weeks i have had plenty to do around the house and im still tired! its almost like im so tired i cant sleep! Help?!?!