Dear friend, welcome and thanks for entrusting your query here at HCM ! You seem to have severe URTI and hence the blood in the sputum. Purulent yellow sputum points to infection. Do you have fever too? Get a CBC done and if the leukocyte count is high, or have fever , you can start antibiotics under medical supervision. I hope you are fully satisfied with the guidance I gave. I would be glad to answer any further queries. Thank you and Good luck !