my saliva have blood?

my saliva have blood.. Fish is no blood the last spit some blood mx in my saliva.. The Pain is my ches and throut. Befor i have a very strong couth but now no couth. I go to the doctor he say there is no problem. The dr process chess xtray and chess ct scan. Its clear but my bleeding saliva is continuous.this bleeding is 2 months. Do u think what. Is this??? Thank u Sorry for my english.