Yeah, you should be putting the recording levels at about 70 and position the mic reasonably close ( a few inches ) from your mouth, but at a 45% degree angle to one side so you won't have problems with pop sounds. You shouldn't be putting the mic at 100% - No wonder, it's picking up all the background noise.
If you aren't already doing this, I recommend you use audacity to record your audio. Before you start talking, leave 5 seconds of silence. Then do your commentary. After recording, you should do the following 2 effects:
1)Normalize (just keep the default settings and click ok) - This will readjust the levels so it's loud enough without distortion.
2)Noise reduction. This gets rid of any background noise. Select the 5 seconds of "silence" I mentioned above, then click on "noise profile" Then come back into the "noise reduction" screen and this time click on "ok"
3) You can now save your audio.