My fissure was discovered during colonoscopy - nobody was able to see it during regular scope . My CRS was able to even make a photo of my "hidden" fissure and show me the bugger ! Fissures can be hidden in skin folds and hard to see. Those fissures are seen only after all folds are "stretched" and explored by very patient and good surgeon.
Best of luck Raul - and lets hope that you will heal without surgery ! When you are fed-up, you always have that option. But, first find excellent CRS - you might need to change couple of them until you find one that you like.
All the best !!!
PS: Try not to sit on the toilet for long time. All poop should go out very fast if it is there - if not, just get up and try later. Sitting for long time just puts extra pressure on your pelvic area .