Hi there...The benefits of quitting smoking are extraordinary. Once you're tobacco-free, your risks of heart disease, lung disease and cancer begin to drop even if you've been smoking for years...pain may be due to respiratory cause or gastritis....Avoid foods that irritate your stomach, especially those that are spicy, acidic, fried or fatty... avoid coffee,tea etc... Avoid stress,consider calming activities, such as meditation, yoga etc...Consult nearest physician once for clinical examination they will do the needful.