The thing with your weight fluctuating is that any retention or anything sitting in your intestines will add weight. I can drop a few kg in weight and cm around my stomach over a few days depending on how I eat. And I can gain it back. Today is one of those days.
It might be better to weigh yourself on a weekly basis rather than a daily ine because of these fluctuations. And carbs aren't all bad, it's the type of carbs. Carbohydrates are what give you energy, it just needs to be complex carbs, so as you said brown rice, etc.