Thank you very much for contacting healthcare magic. You have problem of hemorroid that cause burning sensation while passing stool.Hemorroids are dilated vein that bleed while excessive straining or repeated irritation. Constipation worsen a hemorroid . For hemorroid you have to modify diet like.... Avoid spicy foods and oily foods. Drink more water per day. Take high fiber foods like whole grains, beans,wheat brans etc. ... Avoid excessive straining at toilet. Eat fresh fruits and green vegetables. Avoid alcohol drinking. Bulk forming agent like psyllium can use for constipation. Warm slitz bath is helpful . Topical analgesic ointment helpful to relive a pain. I hope my guidance is helpful to you. Consent a gastroenterologist for further treatment. Thanks.