It's probably the increased activity with school starting and being more busy. It could also be that something has shifted inside you, perhaps you finally reached a state of health in some area that will allow the fat to come off. Maybe your sleep has improved. Maybe you're just more nourished and without realizing it you are moving around more.
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
Starting squat: 45lbs. Heaviest squat: 180 x 2. Heaviest Deadlift: 230 x 2