Hello, and thanks for your medical question on E Health Forum.
Your symptoms are not due to asthma.
From the history provided, it seems that you probably have pneumonia, indicated by the presence of rusty brown sputum.
You might consider to get a chest X ray and blood tests to confirm the diagnosis.
You might need antibiotics and supportive medications for proper treatment.
You might consult your doctor for a physical examination for a definitive diagnosis and prescription of proper medications.
I hope this helps.