If I have bronchitis and tonsillitis and a stuffed up nose could a humidifier help me at all?

Can't hurt. It won't hurt anything. A cough medicine may help, prescription or otc if your doctor didn't give you one. Expect things to get better in 3-7 days with treatment.
Humidifier. Yes a humidifier cam make you more comfortable but antibiotic therapy may be required to effectively eradicate the problem.