Why do i have a chronic cough with clear mucus/phlegm?

Why do I have this cough with congestion? I do not have a stuffy or runny nose... i have had a wet cough -- and I cough up clear mucus/phlegm. I have had this for about a month now! What is it? I don't feel sick otherwise.. i just can't talk without coughing every other sentence...and mucus does come up. Any ideas about what this could be? I don't have insurance (or $300) for a doctor...