Setting a lock requires a password I didn't set

[AC Question]

I've been using a pattern lock screen on my Note4 for months, but a few hours ago the pattern I use wasn't letting me in. Then my backup password wasn't working, so I had to sign into Google. Now, it's stuck at swipe for security and when I try to change it, it asks for confirm password. I only have a few password ideas and none of them work, and there's no way to reset or change it as far as I can see. I'm pretty sure I didn't even set a password for this, and I'm a bit worried this is a virus issue. Has this been encountered before, and can I fix this without a factory reset?