You've got a webcam (with an integrated microphone) and two Voicemeeter devices as settings. Do you have monitoring on? What is your default Windows audio output? From your description it sounds like OBS is capturing its own output and causing feedback, so either OBS is set to output to a device you're also capturing, or your machine is playing output through speakers and then being captured by your webcam's microphone.
I would start by going to the Audio settings and disabling all the devices, and then enable them again one at a time to see when the problem starts to occur.