If I understand it correctly, bronchitis is basically chest congestion and the antibiotics are just to clear up any infection, that congestion might have started, because it was sitting their a long time.
My experience is that the only medication that's worth the side effects is Guafesine syrup, which is called Tussin and is what Rob-i-Tussin was in the first place. (it loosens the plegm and it won't damage your liver!)
Of course,
take a big pot of simmering water, put a towel over your head to make a tent over the water and inhale. (careful of the steam, it's hot!) That's the best instant cure and is basically what an inhaler does (as i understand it and it's side effect free).
Then, of course, the room vaporizer. Vicks makes those and you can buy them at some drugstores for like less than 10 bucks and they don't need any expensive "wicking" filter, like all the humidifiers do and it does just as good a job.
Of course, lots of hot water, steamy showers, steam rooms, ect... get around steam and breath it in.
Avoid cold air, it will constrict your airways. Use a dust mask, if you go outside when it's cold out.
As to cause though, to me it seems like it is usually lifestyle. So, don't smoke. And do lots of cardio (running is ideal). Don't be a big fatty (fattys always huff and puff).
Eating a healthy diet may help, you'll certainly feel better! (three squares a day, using old food pyramid, whole foods (especially grains), lay off sugar, don't worry about salt, just don't eat lots of processed foods). Don't forget to drink your water.