since you are having acute bronchitis
and sinusitis since 3 weeks you have to get the preliminary investigations done to rule out any ongoing infection . Definitive diagnosis can be made only after that.
1. Complete blood count
( in which raised total leucocyte count and raised ESR would point towards an infective focus).
2. Chest X-ray (PA view)
3. Sputum for culture and sensitivity
Treatment would be guided by the investigations:
Ideally you need :
1. Cough expectorant having mucolytic with a bronchodilator
2. A course of antibiotic therapy.
3, Antipyretics such as paracetamol
( in case you are having fever and headache).
For symptomatic relief : saline gargle thrice daily ( for cough and throat irritation
steam inhalation thrice daily (for headache and sinusitis)
Another point which need to be mentioned here is to avoid any triggering agent such as dust, pollution, pollens of flowers.