My dr had me do x rays a week ago and she told me i had bronchitis and a big bubble in my chest cavity. what could that b? she never told me

Hard to say: It's hard to say without seeing the actual images. Since you're a tobacco user, a "bubble" in the chest may mean a bulla which is a focal air bag from destruction of the lung. Sometime it can be from a prior infection or trauma. Did you dr recommend a chest ct to confirm? One other rare possibility is cancer. You may want to ask your dr for more details.