Your loved one relies on you for help. But that does not mean that you cannot seek out help from other people as well. This does not necessarily have to be someone else physically assisting with your loved one, but rather, someone who you can talk with about being a caregiver.
Being solitary is exhausting, but connecting with someone else can be psychologically refreshing. Find someone you can emotionally connect with. That support will help you support your loved one as well.
While other caregivers are an obvious and good choice, this other person can be anybody you trust and who will listen to you. Other caregivers, however, will be able to give more positive feedback about your caregiving methods and even offer ideas on how to improve.
The Cystic Fibrosis Foundation has resources available to help you find someone to confide in. If you cannot find someone local, there are also online support groups.