How could i have the beginning stage of copd when i haven't smoked for very long?

People are different: Some people can smoke for many decades with minimal lung disease while others are so severe they can die or need a lung transplant before they reach age 40. Individual responses vary.

Possibilities...: How many packs you smoke per day as well as the total number of years smoked will determine how much cigarettes your lungs have been exposed to. There are other conditions that you could have as well that can accelerate this process. For example, patients with alpha-1-anti trypsin deficiency will get COPD with a lot less cigarettes smoked than normal smokers of the same age and at a younger age!