So frustrating...

The variation could just be from standing on a different spot on the scale which distributes weight differently. Your weight will fluctuate all the time anyway. If you drink a glass of water, up a pound until it's expelled through sweat, respiration, and urination. In other words, don't let fluctuations get to you. As for your scale, maybe put some marks on your scale to stand in the same spot every time. Also make sure your scale isn't on a rug. That will throw things off too. Weight loss is usually affected more by diet than exercise. That doesn't mean you shouldn't work out, because it absolutely burns calories and can increase your metabolism. But if you only rely on excercise without changing eating habits it will take much longer to lose weight. Also be sure you don't lose more than a pound or two per week in order to stay healthy.