Hello
Difficulty in breathing , tiredness ,mucus in the back of throat , constantly yawing may be to these reasons , these include:
1
Bronchial asthma :Airways hyperresponsiveness that is secondary to inflammatory
airway disease that results in recurrent or chronic episodes of wheeze,
Shortness of breath ( SOB ),
CHEST tightness , &/or cough particularly at night or in the early morning.
2
Bronchiectasis , in this usually patient feels as some mucus is plugged in throat .
However it is very difficult to say something on the behalf of these symptoms .
At present I can say that these are not the symptoms of CANCER.
Anemia may be one such cause of these symptoms.
Cardiac involvement may be the another reason .
In my opinion the best way is to consult a physician and get his opinion because physical examination is important.
Hope this will help you.