I had very similar stool after taking heavy Antibiotics , after a colostomy take down operation. Two things helped me. Diff-Stat probiotic, and chia seeds. The Diff-Stat is specifically made with a pre-biotic and 2 probiotics for use with Antibiotics . The chia adds soluble fiber that firms things up. I take about 2 tea spoons in about 6 oz of water before meals. TJ Max or Marshals had good prices on organic chia. I got the Diff-Stat from eBay, but also available on Amazon
Good Luck
Joe