I am coughing up blood!!! Help!?

i have had flu recently and a very chesty cough. I have been coughing up a lot of phlegm (flem) and very recently i have been getting bits of blood in my phlegm is this because i have been coughing to much? ( my throat feels very dry) or is it something worse because i know coughing up blood can be very serious but i only feel the symptoms from my flu and cold?Help!!!!