merging two Apple ID accounts/emails
Currently apple offers no way of merging accounts. They are rumored to be working on a solution.

In any case you will have to retrieve your Apple ID.
There are 2 ways to do that. You tried the email. the second being the security question:



The last resort would be contacting apple and trying to get them to change the e-mail address of your account (if you have a credit card attached to your account they might be able to authenticate you using this).