Feedback issues

I recently started recording with audacity and a mixer (Lexicon alpha). One recording session everything went fine and the quality was above my expectations. However, a few days later, I start getting feedback through my mic. Not exactly sure where it’s coming from. When i pressed record, the feedback was there regardless of whether or not the mic was plugged in, so its not the mics problem. I don’t know much about recording hardware issues, so any advice would be greatly appreciated.

Try disabling “stereo mix”, aka “wave out”, aka record “what-U-hear” in windows recording devices,
i.e. only record from the USB mixer device, don’t simultaneously record the output from Audacity, (which is “what-U-hear”).
Recording output => feedback.