having a crazy microphone issue and need help

So, about a week ago, while I was in mumble with some friends, my microphone suddenly stopped picking up my voice and instead played my computer's sound to them. I have replaced my motherboard in case that was the problem but no luck there. I've tried both front and back headset and microphone ports, I've tried using other headsets and microphones, and I have tried many other fixes that I looked up on google, all to no avail. I even completely wiped my SSD and reinstalled windows, and the problem still persists. I would be extremely grateful to anyone who can figure out how to fix this problem for me.