Hi, Most of the times Amoxicillin is known to cause loose stools and not the hard one although as an exception to the rule this might have happened with you. Your case looks to be fissure in ano due to hard stool cutting the anal verge. I would advise you the following in such a situation: * High fiber diet * Avoid all the foods and beverages and stress-like conditions which gives constipation * Laxative for softening the stool- never allow the dose too much to cause liquid stools * Sitz bath- very important- just before passing a stool and after passing a stool * Clean the area very clear of the fecal soiling that remains after cleaning; use cotton soaked in the same water to clean * You can apply liquid povidone iodine locally. Apply nothing else. * 5 day course of an antibiotic on prescription of a local doctor * Add probiotics and multivitamins * Avoid stress and mental tensions at any cost; this is a very important factor Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. T. Chandrakant, General Surgeon