email won't work can't change password

my att email which i have had for years keeps asking me for my password and then it wont take it. I cant recieve or send emails because of this. So i tried to go and change the password and it asks me 2 security questions that i made up over 10yrs ago that I dont remember the answers to anymore. All of the sudden today the email stopped working. Like i said it keeps asking me for the password and when i put in my password it says its invaild. so I tried to do remember user id and password help and when i put in my user id ( which is my email address) it says its not vaild ID. What the heck? why today all of the sudden would this happen? How do i fix it. I am in the process of buying a house and I need my emails working, I probably missing important emails now.