From time to time, my stools appear to gritty and sand like in color. some days i have bms all day. what would cause this?

Brown stool: can be indicative of excess fat due to a malabsorption problem. Malabsorption may occur secondary to pancreas or gallbladder dysfunction amongst a host of other reasons.

Grit and sand.: Certainly would go through the digestive tract undigested. Furthermore, cellulose is not digested and the hulls of small grains (brown rice, bulghur, quinoa, many others) would go through and be small fibrous flakes/particles. Bowel activity varies day to day, but if high fiber (see prev sentence) then increased motility results.