my game keeps erasing

Hmm...well, that is quite a problem.

It sounds to me like it has something to do with your game's internal battery, which is a common problem found in the second generation games after about six years. The internal battery is located inside of the cartridge which allows the game to save your progress. After a long while, the battery tends to run out and is no longer able to support saving your game files. It is possible to fix this, however the cartridge must be opened and the battery must be taken out, and a new battery must be soldered in.

The other option, of course, is to just buy a new game. However, if the "new" game is just as old as the other ones, it also runs a risk of the internal battery having problems saving your game.