I was diagnosed with bronchitis&sinusitis yesterday. How do I know if its getting better? I have started caughing up a lot of phlegm. Thanks a lot!

Symptoms of recovery. The sinus pressure and pain will decrease, the fever will abate, the discharge will return to clear and any congestion will become less within 7-14 days.
Tomorrow. Should be experiencing some relief by tomorrow. Sometimes bacteria (if caused by bacteria - could be virus) not sensitive to the chosen antibiotic. If not better, or worse, contact MD.