I Have Been Diagnosed With An Anal Fissure, It Seems

I have been diagnosed with an anal fissure, it seems to heal but then rios back open within a day of being better. I take stool softeners, a laxative, and drink water...nothing seems to be softening stool at all. When I have a bowel movement I have to strain and the stool is excessively large and hard as a rock. What should I do?