Major Recording Problem

hey everyone, i'm starting to rip my hair out, lmao. i have an M-Audio Producer USB mic, and i have Yamaha earphones that i have plugged into that. when i'm in garage band recording, i like to have the moniter on so i can hear myself. lately the headphones have been getting muted and i can't get any sound into them at all. i go into prefrences and change the audio output back to the built in speakers, then switch it back to the mic and it works fine. it starting doing this last night. it only happened once last night, but all day today it's been doing it, and it's very frustrating. if anyone has any advice that would be great, cus i'm going to burn my computer in like ten minutes, haha.