E-mail problem as username? Minecraft (I know, I know, don't judge please)?

When logging into the launcher I try logging in and it says I am using over 16 characters. My email is 17 characters long and my actual username is 5 long. And I did migrate my account. And it is every server I try. So my main question is, how do I login with my mojang email and still be able to use my mine craft username in game?

Read more: E-mail problem as username? Minecraft (I know, I know, don't judge please)?