I had some slight rectal bleeding a few months ago. none since. no abdominal discomfort, but now having thinner stools. sometimes diarrhea also.

IBS: You may have irritable bowel syndrome but rectal blood is abnormal and could have been due to an anal fissure,hemorrhoids,inflammation of the colon, or a growth in the colon. Since you are still having erratic bowel activity, it's advisable to consult your physician or a gastroenterologist for evaluation and treatment. It is a good sign that you have had no further rectal bleeding,however.

See your Dr. asap: rectal bleeding can result from many reasons ranging from not harmful to cancer. Change in bowel habits associated with rectal bleeding is concerning and should be evaluated by a gastroenterologist to start with and referred to a surgeon if needed.