If you eat right and exercise, the weight will come off. That's what the research shows. It just won't come off in any predictable way. There will be ups and downs for reasons that nobody has ever been able to explain.
But you don't really want to lose a pound this week. What you want to do is be healthy for the rest of your life. Right? So keep exercising. Keep eating right. Over time there will be progress.
Are you tracking your food intake? Sometimes foods that we think of as healthy that are loaded with hidden calories or fat. Other than that, don't let a blip on the scale throw you off course. If I had to guess, I would think that your "before" weight was taken when you were dehydrated. If you have been exercising more you may be drinking more. Or you may be drinking more water for general health.
"There's treasure everywhere." Hobbes, in Calvin and Hobbes