Sorry to hear about your videos not showing up.  How many clips have you attempted to upload?  If you have yet try it, unlink and relink your YouTube account and see if your videos will properly upload.

I also recommend checking the default YouTube Channels for MW3 to see if anything is shown there.

Xbox 360: http://www.youtube.com/user/360codmw3?feature=results_main

PlayStation 3: http://www.youtube.com/user/ps3codmw3?feature=results_main

Also try unlinking your account and see if any videos will be uploaded to the default channel.  Again I do apologize for the situation.  Thanks!^RT