Q: I cant log in    changed password and cant log in w new or old password

What year Macbook and what operating system are you running. As this will determine what to do. And what screen are you getting at startup.  https://support.apple.com/en-us/HT204156

Hello, I have the same problem as jeveridge, and I'm using FileVault login? What can I do now?

Again. What computer and year. What operating system. Did you set a different password for FileVault the your administrator password.

It is MacBook Pro, I think is 2012, I'm not really sure, the operating system is Mavericks, I think. and about the password that you are talking about, I don't know because my son set up that and I'm guessing they are different

When turning on FileVault, it asks to set a master password.  The best way is to leave it the same as the admin password.  If you need the FileVault password before you can get to the login screen. You would need to erase and reinstall the operating system. As any options such as single user or safe mode would need the password to even start. You can try this and see if it works.  https://derflounder.wordpress.com/2015/05/27/stopping-your-mac-from-booting-to-t he-filevault-2  https://support.apple.com/en-us/HT204837 I would suggest that if you get the FileVault password reset, that you go to systems preferences security and turn it off.

Okay , I got it , thanks for your help!!'