Garagband...automatically adjusting recording levels?

I'm a podcaster, and I talk over Skype and record my audio file using Garageband. When I first started doing this on my iMac, everything was fine. I would set the recording level of my mic with the slider in Garageband, and there it would stay. Now, for whatever reason, the slider is constantly moving on its own. NOTHING is set to automatically adjust, and I can't figure out why this is happening. I use to encounter the same exact issue on Windows when using Skype, but within Skype for Windows there is an option you have to turn off that allows "Skype to automatically adjust audio". There is no such option on the Mac version (at least not that I can find) of Skype.

Furthermore, I do NOT have this issue at all when recording on my MacBook.

Does anyone have any ideas or recommendations?