Soft thin stools, sometimes firm & medium size, followed by continued slow involuntary leaking of more soft to liquid stool for 5 minutes. cause?

Constipation, bowel: Often constipation with liquid leaking around stool causes this, but there are many causes and treatments depending upon cause. Most commonly a good high fiber diet to bulk stools with adequate liquids is effective but if a more significant problem exists underlying then other issues need evaluated and treated. Look at http://www.Med.Unc.Edu/ibs/files/educational-gi-brochures/bowel%20leakage.Pdf.