Rectal bleeding should always be medically investigated until a concrete cause is found. Type rectal bleeding into google and click on to one of the many sites - the Medicinenet site is especially informative. Then you will be better prepared for your next medical consultation. Unless the cause can be identified as one of the minor ones (e.g. anal fissure, haemorrhoids etc etc - and this means a firm diagnosis not a statement such as "well it looks as if it might be .....") then I suggest that you request a colonoscopy.