What Causes Itching In Anus With Dark Coloured Blood?

Hi my anus itches with dark coloured blood on tissue after passing stool sore after wiping bowl movements been varying for some time now. I am 48 years old about 6ft tall and a weight of about 15 and a half stone I have a lot of acid reflux for which my G.P put me on Ranitadine and Gastrocote I am also on Fluoxetine for Depression. I also take inhalers for astmah and my Father died from Prostrate Cancer in 1999 and my Mother from Pnumonia in 2009 she also suffered from angina and thyroid problems.