Sure, it makes sense that you hear your wheezing more when you are sitting/laying down - you can probably hear a lot of things better when you are still! Although you might also want to pay attention to your surroundings - is there something nearby that might be triggering your asthma? A cat, for instance.

Use your inhaler when you are wheezing or when your chest starts to feel tight. Or when you know that you are going to be exposed to one of your triggers. However: I just looked up your inhaler on the internet. Symbicort is a controller medication. You use it every day, whether or not you are having symptoms; it minimizes the symptoms. It will NOT stop your wheezing or other symptoms once they start. That's why you need a rescue medication like albuterol or xopenex. You might only use your rescue drug once or twice a week - just when you need it.