Fit individual w/ consistent diet&exercise regimen &very stable weight, but w/recent unexplained loss of 5lbs. haven't changed habits. cancer?see doc?

See doc, don't worry: Unintended weight loss can occur with a lot of conditions, most of which are less serious than cancer. For example, it can be a symptom of anxiety or depression. It makes sense to see a doc if you're worried about it, but I definitely wouldn't jump to any premature conclusions about what's causing it (after all, if it's anxiety you'll just aggravate the problem!).