Blood in salaiva in early morning.

I am finding red or yellow colour salaiva in the morning every day for last 3week I am not sure if it is blood or not. Last month I was coughing up little amount of blood I went to the doctor did the rests report came with some infection in chest. Taken antibiotics it was ok. But my cough is not completely went away sill I cough some times and some times I find little blood in the salaiva. I have dry cough only no mucus production. I went to the doctor again. Did tests chest x-ray, CBC but every this is normal this time. But still I am coughing up since last 2 months it is not completely going away sometimes I have pain in chest also but no shortness of breath. Is it something serious do I need to do any other tests or consult any specialist? How long it takes to recover from blood in cough because of infection?