Yahoo won't allow me to sign in

Hello,

Yahoo won't let me sign in to my email address.

I remember my Yahoo ID and passwords just fine. But Yahoo won't let me sign in by forcing me to answer all these security questions. I don't remember any answers to the questions. I also don't remember my alternative email.

When I first registered that email, I didn't enter any cell phone numbers, so they can't send me any recovery code via cell phone. What can I do?

EDIT: I still can sign in to Yahoo Messenger though. Is there a way to access my mail box and change personal information through Yahoo Messenger?

Please help me!