In view of history of cystic fibrosis
, you are prone to develop repeated chest infections. There may be some collection in that part of the lung though upper lungs are drained well in view of there location. You may be feeling the movements of these secretions though lungs do not have any sensory supply and it`s not easy to feel such things but a patient with chronic disease like your`s may be able to tell sometimes. Another possibility of recurrent bleeding (you have already undergone bronchial artery
embolization for an episode) have to be kept in mind. I suggest you consult your pulmonologist who can guide you correctly.