It is all about the consistency...
Some say that the belly button measurement is best in terms of an over all health measurement. It is a better gage of "belly fat" or visceral fat in your abdominal cavity. But since you are about as motivated a "loser" as there ever has been, pick a place and just stick with it.
BTW many folks have noted that the waist is about the last place they notice changes, so don't forget to measure other areas too.
2.5 years, 45 pounds later... 128ish pounds