my gameboy suddenly stopped turning on and its also not reading my gameboy advance sp games anymore
A wide range of things could be wrong with the Gameboy (i.e. broken power switch connector). I suggest that you simply get another one, since there is no way to know exactly what could be wrong (assuming the batteries are fine).
You can also check this compatibility chart about the GBA games.
The battery could be dead, as in, it won't recharge anymore. Rechargable batteries don't last forever and dwindle down after constant usage. This is noticable on my Nintendo DSi which has had extensive recharge cycle and no longer puts out the super long charge it used to have.
Game Boy Advance SP's are realitively cheap now a days. If you don't want to buy a new one, you could always buy a Nintendo DS Lite which plays Gameboy Advance games.