I guess this confession can do even worse in your situation. You say that you used someone else's posts passing them off as your own. This is what plagiarism is, and plagiarism is strictly forbidden by rules.
No sir, he wrote some post for me which was not used anywhere in any place just like some one write writing article for you. I don't think it will be refer to pilgirarism
I'm not the one who decides if it will be considered so or the other way. I don't even know if to report anything and if so then what. But when moderators will see your confession they'll do what they'll consider right in this situation.