Several things that might be happening:
- Make sure you use the same scale at the same time of day, and wear the same amount of colthing.
- Urinate before you weigh yourself. A pint of urine (not a real large amount)weighs one pound.
- You might be recording the amount you eat inaccurately. Many studies have shown that recall of food intake is very unreliable. Even food diaries are fairly inaccurate. Make sure you include drinks as well as solid food.
- Your fluctuations may be due to water retention rather than fat accumulation. If I eat salty processed food, my weight is one or more pounds heavier the next day. Hormonal variations can make adifference too.
My advice is to keep weighing yourself, and record the weights. After a few weeks/months you'll learn to interpret the results better. People who weigh themselves regularly are more likely to keep the weight off.