I used to have pneumonia and asthma, now i have no energy for physical activities, could it be from underdeveloped lungs?

Yes: Yes, it could happened as a complication of chronic lung disease. But u can restore your lungs function by duin g special lung exercises.

Continued asthma: Asthma does not automatically go away after childhood (especially in someone who smokes). Any adult who has no energy for physical activities needs to talk to their doctor. Depending on what the doctor finds, special testing and treatment can be helpful. In someone who had asthma as a child, under-treated adult asthma is the most likely cause. It may respond very well to pretty simple treatment.