Keep calm..!
You have 2 choices ^^ :
Go guildwars.com -> support -> web support -> Live help
Now : when you contact them tell them your problem.
1st choice : If you still have the serial number you used to create your account/expand it give it to them. They will send the informations of your account on to whatever e-mail adress you wish.
2nd choice : Tell them the e-mail adress your account used to belong to AND tell them your actual physical (real life) adress you wrote in the account iformation.
Also giving them information about certain payments you ensured might help.
P.S. : I was in a similar situation and I used the 2nd choice and got my account back

Hope it help and have fun! ^^