My account was hacked.
All you have to do is change your password. After password is changed do not check the box for password to be saved. This means that each time you go into your e-mail account you will have to manually enter your password. I went through the same thing as you, at first it was a pain to always have to enter your password but the agrivation it saved was well worth the few seconds it took to enter the password. Hope this helps.