All reply emails are being directed to a different email - my account was hacked - how do I fix this?

[Steve]

My email address was hacked and all of my contacts were sent an email stating that I was in trouble while traveling in Europe (not true) The email stated that I needed money to get back home. Ever since this happened, when I now send out any emails to anyone, my return email address populates as a different email address and all reply emails are not coming back to me they are going to a different email address that is almost exactly spelled like mine except with an added letter in the email address. Any suggestions on how to get this fixed?