If you are in your fifties, it could be hormonal changes. If you are taking Iodine, it could also be your hormones kicking in. And it may simply be that your body is fighting off the giardia. Eventually your body will get adjusted and it will stop. While it's happening, please consider helping your wife out by changing the sheets. She will greatly appreciate the gesture, and it will prevent any resentments from arising during your healing process.