Can't Login to My Website

A few days ago I went to login to my website via wp-login.php when I saw an error message saying “Error: Cookies are blocked due to unexpected output.” I thought nothing of it and went to enter my username and password, but for whatever reason it was telling me that my password was incorrect, so I decided to just reset my password. When I got the email and clicked on the link I got the white screen of death.

I’ve been trying to login via wp-admin (which isn’t displaying the error message that wp-login is), but it still says my password is incorrect.

The strange thing is that even though it says my password is incorrect, it’s not counting it against the number of login attempts. I could enter my password 10 times and all it says is “Incorrect username or password”. But if I enter any other password, even it’s the same password multiple times, then it starts saying “X number of attempts remaining”, it’s almost as if it knows that my original password is right, but it just won’t accept it.

Any help would be greatly appreciated. I’m not particularly tech savy, so instructions in layman’s terms would be extremely helpful. Thank you.

((Also as a side note, I don’t remember exactly for sure which version of WP I’m using, since I don’t remember if I updated before I got locked out, but I’m positive I’m using at least version 4.4.))