thanks for asking your question I completely understand your question cough with yellow sputum means their is an infection of the respiratory tract , may b upper or lower resp tract infection. so u need to take some antibiotic like cefexime for a week or two after consulting a pulmonologist. pain in butt may be due to excessive pressure applied during a cough , muscles contract. if this problem persists you can take consultation from a surgeon if u smoke , u have to quit smoking as early as possible thanks /regards feel freet to ask more questions may god bless you with good health