First of all I'm not a doctor, and I won't be giving any medical advice or tips on sickness of any type. Here's what I will share with you that you should consider doing when you're sick.
1.) Keep in mind your health and those around you. Germs are everywhere and we all take risks being exposed to them. Do your best to minimize others people's exposure when you know you're sick.
2.) Jump on the communication train. Either you or someone who is able to speak for you needs to let your Director and the other folks on the production team know you're sick. Communicate with how long and discuss how it may impact what you're currently a part of. If they have to replace you, it sucks, but that show will have to go on.
3.) Take a break from auditioning while you recover. I know you'll probably be better by the time that project comes around, but other projects will be there too. It's best for you to allow yourself time to get better.
4.) Do what you want during this time. You don't need to fill the void with trying to study or work on your craft. It's ok to take whatever time you need to focus on getting better and taking care of the other things happening in your life.
5.) Give yourself some grace. Life happens. Things like getting sick can feel like they come out of nowhere. You can't life in a bubble of perfection. Have a plan for when you or someone in your family gets sick that is doable and can help you through.
Take your vitamins, wash your hands, and don't lick walls. Good luck and take care!