Well make sure you eat something before you take the chantix, and stay away from anything bubbly or caffinated (sodas) until after about an hour. That helped me witht the side effects. Although, I havn't completly stopped taking Chantix, I am taking 1 tab in the morning, and none at night. The insomnia was killing me. As far as upset stomach goes, I take mine about 10 minutes after eating a bagle and do fine. Good luck.