You should go to
Mojang's website and log in with your email address and password. (If you didn't lose them)
When you're logged in, you'll have to go to the
Settings tab.
If that went right, you'll see some options to change your email/password/security questions.
Make sure to change your
security questions and your
password to something else that only YOU know (and remembers).
NOTE: The best thing to do for you password is to change it to something you haven't used on other online accounts yet.
If you don't have access to the password for the account, you can still change it with
this link. Fill in your email address and an email with information will be sent to that email address.
If you don't have access to the email address anymore, you can try to follow
these steps.
If you don't have access to the security questions, you can try to follow
these steps.
Feel free to ask anything by clicking the
Reply button on the right of this answer.
Hope this helped you!
