not able to access my account
 

HELP-I have had a Yahoo email account for 7 years. Starting about 2 months ago I have not been able to access my account. It keeps saying 'Invalid address or password'. I am also unable to correctly answer my security question. The account has been tampered with in some way and I need to get back in. I have very important emails that come through to me daily for business. I really need this problem rectified...HELP!!!!!