Here are some reasons for "unexplained" and "I'm not cheating" weight gains:

-unsuspected salt in the previous 4 days of food.
-unsuspected carbs in the previous 4 days of food.
-water retention from medication, heat, exercise, stress, infection, exertion, TOM
-muscles making repairs or increasing in weight from exercise.
-headache tablets of any kind.
-changes in the weather
-decreased calories or carbs (not on purpose) scares the body into thinking the gravy train is over and famine is coming. Circle the wagons! Consever body fat!
- the whoosh fairy is in Australia and will not be around your way until next week.
-your body just feels like it.
-someone is soaking a voodoo doll in lead because they are jealous of how much you have already lost.

The best way through these times - even gaining a few pounds of water - is to keep on plan for the next 2 weeks. And stay away from the scales. Try on your tightest pair of pants every 2nd day. Inches can go while the "metal monster" refuses to move.