Coughing had it for nearly 3 wks now?

Cough: Likely allergies/ seasonal with post nasal drip or infection with mycoplasma that requires antibiotics. If smoker consider lung lesion, if blood streaked and you have exposure consider TB rarely rare autoimmune conditions like sarcoid or if immunocompromised PCP( may be short breathe) Would elevate head of bed at night try antihistamines and follow up with with doctor urgent care

See a doctor: You need to see your doctor who will examine your chest and possibly arrange for sputum samples to be sent to the lab and possibly organised Chest X Rays and blood tests if needed,