I'm so sorry worrier. Please try to not blame yourself. It is the job of the professionals to know what they are doing in order to avoid these sorts of things. I wonder if doing some pelvic floor muscle training exercises might help you. If there is a gutter where the internal sphincter was cut then maybe bulking up the surrounding muscles will help to form more of a seal. I have read that the internal sphincter only contributes 55 or so % to resting tone down there. In the meantime, the internal sphincter should regain some strength. I also read somewhere that application of phenylephrine hcl is thought to tighten that muscle up some. Here is Canada it is in a hemorrhoid ointment (http://www.preparationh.com/products/cooling-gel)
I also read about anoplasty procedures and fillers that can be used. There is also sphincteroplasty. I wonder who you could talk to about that. I suppose nobody will want to talk about that until some time has passed and it is determined to be a long-term problem. Do you 'feel' quite loose back there? Did your fissure heal too? Do you know how much of your sphincter they cut?
I, myself am worried that I have a lot of deformed tissue down there and it hurts more that my fissure did. Think i will have to get it removed which is to sign up for basically a hemorrhoidectomy (pain wise). I am feeling really frustrated and pissed with Doctors. I put my trust in him and feel totally let down. I can definitely relate. I also wonder if i have a gutter too.
Keep your chin up Worrier It's got to get better from here.