You mean forged? Nobody can answer it for you and it never happened to me.
Find ways to talk to your former boyfriend but I think you need start damage control:
create new email address and contact administration above websites to let them know about your lost passwords to freeze activities there but if to be honest it will not stop somebody who is so determine to use your name to just annoy you.

You need to talk to him to find out what he wants and make desision based on your conversation. Alternative to it only law inforcements involment or ignore him at all if you can.