Brown lumps in sputum can be due to excessive smoking
as the resin in the cigarette sticks to the mucus. It may also be due to disease like bronchitis
or lung cancer
. Blood investigations are usually normal in initial stages. Since you have not been feeling well, I would advise you to get a complete check-up done and not neglect this. Please also consider giving up smoking again, as whatever may be the cause of your symptoms, smoking will just aggravate it.