Re: coughing dark chunks of phlegm
This could be very minor - BUT IF you ALSO have a Fever for more than One Day, go see a Doc.
But without fever, try lots of Immune boosters like Goldenseal, Olive Leaf Extract, Garlic, Turmeric, Echinacea and the basic Vitamins A, B, and C. And Drink lots of Fluids.
Sounds like you could have Bronchitis - there are two kinds - Viral and Bacterial - If you have the Viral form, Anti-Biotics wont help at all. If you have bacterial form of Bronchitis then a short course of anti-biotics might clear it all up.
If you have the Viral variation then keep yourself in good health and it should pass in 1 to 3 weeks.
If you are a smoker then things could take longer.