Rectal Bleeding, bright red blood?

Hi I know this might be to much information but I am worried. Every time I use the toilet I am bleeding bright red blood with constipation/hard black stools with blood also in the stools. It doesn't hurt but is just stressful because it is hard to use the loo. Please help I went to my doctors and he gave me laxatives which have not changed anything instead they just burn my stomach. I have had this problem for over a year and my diet is very healthy I eat a lot of fruit and fibre but it still doesn't help anything. Is this cancer? How can I stop it? Thank You x