My prayers. Seek professional help, for piece of mind. Get evidence for your Doctor. Use a Toiletta. You buy them on the internet. A Bristol Stool Chart will give you a starting point. Tar stools are caused from internal bleeding. Thin stools could be your health and normal. Everyone is different. Transit time shoud be around 8 to 12 hours. That is the time from teeth to toilet. The chart has helped me out a lot. The Toiletta allows me to pull back on that part and look for blood. That part of my stool is so hard and lumpy. It is like rocks. Not sure if it is my fiber or my water consumption that is causing that. I hope this helps you to the road of knowledge and recovery. Sorry, I had to shorten this to make it fit.