I can't join my account

I few weeks ago I create an account using my facebook, but now when I try to enter the account via facebook again it lead me to the sing up page, I try logging using my username but it says that I have to join that account using my google account, but I never linked my google account, so I want to know if is possibly to enter again in my account maybe changing the facebook account to a normal one or just get the world back that we used in the server and make another account, thanks