A few days ago i experienced the worst stomach flu of my life. the pain in my back and chest is unbearable. it hurts to breath and talk. what do i do?

Pleuresy or: Pleuritis. That is inflammation of the linings of the lungs. When get inflamed rubbing to each other during breathing cause pain. Take otc Ibuprofen and follow the instruction on the label. If pain is severe you need prescription strength pain medication. Having said that to be on the safe side i still advise you to see your family doctor to get your chest listened and may be a chest x-ray.