Forgotten my security questions so now can't buy off iTunes. Help

If you have a rescue email address (which is not the same thing as an alternate email address) on your account then the steps on this page will give you a reset link on your account : http://support.apple.com/kb/HT6170

If you don't have a rescue email address (you won't be able to add one until you can answer your questions) then you will need to contact Support in your country to get the questions reset.

Contacting Apple about account security : http://support.apple.com/kb/HT5699

When they've been reset (and if you don't already have a rescue email address) you can then use the steps on this page to add a rescue email address for potential future use : http://support.apple.com/kb/HT5620

Or, if it's available in your country, you could change to 2-step verification : http://support.apple.com/kb/HT5570