Second hand smoker's cough and heavy smoking parents?

My parents are really heavy smokers, and I sporadically developed a very painful, loud, and hard chest cough that also has phlegm. The phlegm is yellow, and my cough isn't as bad, and almost non existent at times when I'm outside of the house. Yet, when I try to tell them this, they get mad at me and say I'm just sick. I'm not old enough to drive myself to the doctor, and they won't take me. What should I do? Also, I haven't been able to get outside because it's been raining the last few days, so if you're wondering why I haven't done that, I have.