help my email has stopped working

You should try resetting your password via the Email Website you are using.

If that doesnt work I would try adding a Test account to see if any account is adding.

Make sure your typing in your password correctly, passwords are CaSe SenSiTivE

What E-Mail provider are you using? Gmail? Hotmail? Yahoo?

If it's Gmail it could because you haven't set an application specific password for your settings. I won't go in depth on how to that unless you have Gmail. Let me know.

Are you using a POP account? If yes, check this article: iPhone and iPod touch: 'Mailbox Locked', account is in use on another device, or prompt to re-enter POP3 password

Or try the general troubleshooting here: iOS: Unable to send or receive Mail or What to ask if you're having issues sending, receiving, or configuring Mail