Hi dear if this bleed is not associated with pain than is generally due to piles and quantity of blood should be more. If this is associated with pain and quantity is less than this is due to fissure.  This may be due to sigmoid colitis in your case. You should avoid constipation, as this is the cause for piles/ Fissure. it's better to get evaluated , a short scopy done to rule out the underline problem. Take salads in each diet. Take plenty of water. Get your self evaluated soon. Take care.