Never fear. for i am here!
Sorry i'm a bit late with this post D:
For anyone still struggling with this...
1] Go to https://account.mojang.com/migrate
2] Migrate your account to mojang
3] While you are migrating your account, it should ask what email you want to use. Click 'add new one' (or something - from memory) and add the new email you wish to use...
4] If you did not do that, you can log in, go to [account name / email ] > settings
5] Click Email: - - - - - - -- - - - - - EDIT
6] Do as instructed.
7] After editing your email, you will have to log in with the email as the username