My lung sometimes feels tight. does this mean that i have asthma?

Perhaps: Coughing, wheezing, chest tightness & chest pain are symptoms of asthma. When asthma is mild symptoms may not be present all the time so "sometimes" is an important point when talking about asthma. Your physician or health care provider can take a complete history, perform a physical examination, assess your response to bronchodilators & perform pulmonary function testing to make the diagnosis.

Perhaps...: I would need you to clarify exactly what you mean by "tight." then, there are pulmonary function tests that can be done to determine whether this symptom is due to asthma or something else entirely. These tests would be needed since the treatment would be different depending on the precise etiology of your symptoms. Good luck.