If i sleep on chest side i get breathlessness in minutes wt cud be this ?

See a doctor: I suggest that you make an appointment to set your doctor. Symptom of breathlessness is not normal and needs evaluation.

Pericardium: The pericardium, the fine liner around the heart, can be inflamed or filled with fluid. This can be the cause of such symptoms. Similarly, fluid or inflammation of the pleura, the lining around the lung, can produce similar symptoms.