Coughing problem. With brown spek in it.

I am dealing with spitting problem from last 4 weeks , i feel urge to clear my throat frequently and it's not pure phlegm sometime it is phelgm but mostly it is saliva and i don't have any fever chills nose blockage and difficulty to breath etc When i wake up in morning my throat gets filled with phelgm which i have to clear and spit it mostly white sticky substance I consulted an ENT on practo because of curfew and corona it's becoming difficult to get to a doctor physically and he provisional diagnosis it sinusitis and post nasal drip and give me medication for five days and steam inhalation it improves things a little in day time but in morning my throat still gets filled with phelgm and sometimes I'm spitting saliva with something black or brown in it it is not fully brown or black it is  a little spek and i told him this and my condition is not getting normal ,  he told me to consult a respiratory physician I've clicked images of my spit with brown spek in it .