Hello Do not worry nothing serious I don’t know which country you belong to but in some Asian Countries there is a worm infection around anus which can give this feeling .Get a stool examination Microscopic done if it is normal Go to a general surgeon and get a local examination of anus done If all above are normal apply any soothing skin/mucosal cream after passing stool and in night . Take one or two courses of de-worming drug from your doctor otherwise also and request him to write soothing cream also You have referred to your sitting posture ;get some cushion to sit on Take care Dr Lal Psychiatrist