How can I fight a phlegm buildup besides coughing it up gradually?

I'm driving my girlfriend crazy with my constant hacking and spitting out phlegm into a paper cup. She thinks it's gross and the constant coughing gives her a headache. She tells me to take a cough drop, but that does nothing for the actual phlegm problem. Also, sometimes the coughing jags become so intense that my lower back and (I guess) kidneys hurt, and my bones are hurting because I've been avoiding milk so that I don't make more phlegm and therefore I'm not getting my calcium. How do I deal with this problem?