Hi The reason for chest discomfort can be due to bronchitis or bronchospasm or even gastric irritation or cardiac problem.And it is not evident in your quetion that why you took narcotic pain reliever percocet ,prostaglandin cytotec and doxycycline antibiotic.Better to avoid all these drugs with out reason and with out the advice of a doctor because all these drugs can cause serious adverse effects if not used judiciously.Better to have a physician examination and rule out your problem.Apply warm water bags on your chest.It might give you relief.Let me know if you have any further query thanks