
No I haven't had/experienced what you are going thru, but I do have a question..
I'm a bit comfused with the medical term you are using. The fissure. Is it a tare in the skin lining/anus opening? Is the condition farther up in the lower colon?
Had the condition healed and you've reinjured yourself?
If the condition had not heal and you had sex, then of course it will take much longer to heal.
On a nother note:
Sometimes the skin/area looses it's elasticity after a surgery/wound, or scar tissue forms. So, this also would explain, retaring/spliting the area. If this is the case, you may not ever have the freedom you've enjoyed for so long.
Perhap when having this type of sex, from now on, you will have to be mindful of the size of guy you're with.