Er dx me with a 2cm opacity on lower right lobe of lung on ct today. 3 mos ago everything was fine on imaging just costochondritis. no hx of lung issues. gave me doxy for pneumonia. only symptoms is chest pain. i thought pneumonia had more symptoms?

Time to move out of ER as follow up with your primary care doc or pulmonary specialist with access to your ER records is now needed. Your chest pain may or may not be related to the CT findings. If inhaling, smoking, etc stop at least until a proper diagnosis is formulated.

I think this opacity is almost large enough to be considered a lung mass & is at least a nodule.. I urge you to consult a pulmonologist for evaluation and advice. In this manner any testing deemed appropriate will be ordered and you'll have peace of mind.