So i haven't played this in like 2 years, so i decided to start it up and play some online. But to my luck, it was registered first to my old steam account, which i completely forgot which email i used and what the password is. Does this mean il never be able to play online without repurchasing?

How many email address have you?
If you have an old Steam installation, under the steamapps folder you should have at least 2 folders:
SourceMod and a folder with your Steam user name.
Old Steam installer picked up the email account used when registering the game.
Try that.
For what about the password...
a 22 years old guy should not have such memory issues...
otherwise quit smoking poisoned "stuff"....