If you are adding muscle then that weighs more than fat, so yes it is possible to lose fat yet remain the same weight or even go up. Although it's more often the case that (unless you have been trying to put on muscle) there has been a misunderstanding regarding the connection between healthy and low energy food. Healthy is good but need not be low in calories. One should note what one is consuming.
2.5 lbs is a loss in any case. One ought not expect a large drop in short time, that wouldn't be healthy anyway.
Be aware, exercise for weight loss isn't that effective. One has to do a lot of exercise to burn off the calories in a simple snack. Intake is key. But I think you just need to adjust your short term expectations.