Passing stools with burning sensation

Hi i get 3-4 stools daily since many years. i did not bother as it never causes any problem for me of late i started getting burning sensation in stools while defecating. the after effect is iam unable to sit at any surface because of the burning sensation. I think is it due to acidic nature of stools or anal fissures caused due to excessive stools; or is it IBS or Carcinoma? Otherwise iam normal, without any disease i maintain strict dietary regimen with lots of veggies & fruits. I do not have any habits for that matter? Kindly suggest me what should i do? I apply povidine iodine+ sucralfate+Tinidazole combination ointment in the anal region to avoid further damage to that area. I uses Lactobacillus & Normetrogyl tablets occaisionally to get relieve from access stools.