Login not working after update

Yesterday I updated my Mac with the latest OS. Today I cannot log in past the lock screen as it is not accepting my password. I did not change any passwords while updating the OS. I initially updated OS after downloading, clean my Mac software, because I was getting Safari pop-ups. My computer seem to run a lot smoother after that. Again, I did not change any passwords, but I cannot log into my computer now after restarting it. Also I have never set up a recovery key. Please help.