My audio changed drastically and I don't know why

I recorded some audio last week that comes in really clear. I recorded audio this week that comes in really quiet. I changed nothing in the settings but I can’t figure out how to get the audio back to where it was a week ago, or even a few days ago. Can someone help?

I changed nothing in the settings but I can’t figure out how to get the audio back to where it was a week ago,

Did you use Skype or run any applications that might have monkeyed with your audio settings?

What are you recording? Streaming audio? The microphone built-into your laptop? From a USB turntable???