Fecal incontinence

I had surgery to repair an anal fistula in 1988. I was told by a doctor years later that I had what is a keyhole anal diformity, most likely do to the surgery. On occasion, when I have a strong urge to have a bowel movement, I cannot hold it for more than a minute or two. This is an infrequent occurrence. I have learned to clean myself out before leaving my home so I will not have the need to go. Needless to say this can cause major issues when away from a bathroom. I find that taking 1 or 2 immodium tablets prevents the urgency. Any suggestions would be greatly appreciated!