i had EXACTLY the same problem, when i was your age!!!
It really is a pain, some days its worse than others, n when you really push yourself it hurts when you make twisting movements and what not.
I tried heat pads, rubs, everything!
But, (yes there is a but)! I found that sleeping on the floor really helps, i did it for about two months and then brought a hard really good matress and it helped alot! Also give hot baths a try, they really help to ease the muscles in your back!
Also, i know it sounds obvious, but try to thouroughly warm up before you train, especially weights! Try adding back extensions to your routine, and superman holds, as the will help to increase your core strength around the lumbar region!!! I also found that deads didnt help, so ease of the deads and the bent over rows if you do them, as the place the back at risk!!!
hope this info has been helpful, let me know how ur doin!!