Why am i prone to bronchitis?

the slightest cold for me turns into bronchitis. i read a thread, and apparently it happens to other people too. however, the majority of the people were either smokers or had asthma; i fall into neither category. how exactly can one even be prone to bronchitis? it's really obnoxious because when a cold is going around campus, other people take some cold meds and go through their day with the sniffles; meanwhile, i'm coughing up phlegm with a fever, and it takes at least a week for me to get back on my feet and feel functional again.