IT WORKED! Thank you so much
Here what happened exactly for those who have the same problem:
I reset the password in recovery mode, and restarted the computer, and now I can see another option at the login screen where i can type my user name and password, if your old username doesn't work, instead type "root" in the username, and the new password you just reset, and you'll get access to a new administrator account, not your old account that got disappeared. So now what you want to do is go to system preferences>accounts and groups, and make a new account with the same account name you lost, and a message will appear saying that "a folder with the same name already exists, do you want to write over it?" Or something like that, just agree to it, now log out and you can see your old account, log in and you'll see everything just like the way you left it!! Yay!
Ps: even tho everything was back in place, my mac doesn't function the way it used to, it's super slow and apps keep crashing.. I backed it up and I will reset it and see what happens