Why no weight loss after 3 months of exercise?

To lose weight, you just be exercising and burning off more than you are consuming. If you are not an a diet and lowering what yu consume, then you are just exerciseing that food or energy off and not tapping into stored fat on your body. It could be that you have lost fat, but gained muscle mass, too. Otherwise, your workout may not be targeting the right area to lose weight in.