Does Not Accept Password

I have a Mid-2012 Macbook pro. When I try to login it doesn't accept my password, and I am pretty sure it is my password. I tried multiple times, it still doesn't accept it. I know you do Command-S and that stuff, but when I press it, it doesn't go to it. Even with others like Safe Mode, or Recovery Mode it doesn´t go to there. What should I do ?