Could I have gotten hearing loss from being a waitress in a bar with loud bands?

Yes, you could. Chronic exposure to loud music or machinery is a very common cause of high frequency hearing loss. Avoid spending too much time near the band, and wear headphones when using noisy equipment. For a more thorough discussion, see http://www. Richmondent. Com/ear-nose-throat/ears-hearing. Php.
Yes. The loud bands could produce enough noise to cause a high frequency hearing loss. Obtain an audiogram. Also you may need to protect your inner ears from progressive hearing loss by using some form of ear plugs. As a waitress, I know you need to hear. But your hearing is more important. Get a job where there is no loud band noises.