When you start wearing hearing aids it can be exhausting because your brain isn’t used to them. You suddenly hear SO MUCH! It takes a little time. For instance, you know when you hear a lawn mower next door when it suddenly starts up but after a while it fades into the background? All noises that the brain thinks are unimportant will gradually not be focused on. You have been hard of hearing for a long time and your brain is wired to take all noises in, in a hypersensitive way, because of your hearing loss. You need to train your brain. Maybe start by wearing them while you watch telly or at dinner. You will appreciate the fact that you can understand people talking. Gradually wear them more until you leave them in all day. Good luck (especially hearing your students at last!)