That means you ended in a "server" version (so with no working desktop).
The login in the normal login you see on a server. But it should let you log in with any of your accounts. If it does not more is wrong.
Boot into a live dvd and mount the disk that has your /home/ on it. Go to /home/$USER/ and do a
tail -n 100 .xsession-errors and see if it holds errors.
Next check with
ls -la in /home/$USER/ that the properties are ...
-rw------- 1 rinzwind rinzwind 57 aug 2 09:03 .Xauthority
-rw------- 1 rinzwind rinzwind 153 aug 2 09:03 .xsession-errors
(the name rinzwind should be your user name) for these 2 files.
Edit your question with the result. If you want we can see if we can get it back up by fixing any errors you found. I assume your password will be correct and it kicks you back to login due to problems with the login part.
If you need it start making a backup of your files now.
You could then forget about it all and re-install. That would get you back and restoring your backup will get you your files back too. All you will be missing is software you installed and settings you changed.