Where is it saying you have to buy the game again?
If you still have your CD Key, you can re-install the game with that and log in with your existing account.
If you don't have your key then email
support@reverieworld.com from the email address you registered in-game with and we can look up your key and username. You can use your key to recover your password in-game (it will send you an email) or we can reset it for you.
EDIT: I've looked up your username and key and emailed them to the email address you registered with (same address as you use for the forum)