unlike a physical illness or disabilities where there are clearly defined caregiving tasks (e.g., helping with mobility, bathing, administering medication), it's primarily emotional/mental burden where you can't just ask a stranger to stop by and help out for a couple days (not to say that there isn't a mental/emotional burden with all forms of caregiving).
couple that with the social stigma many people feel about mental health issues, you will most likely have to fulfill your caregiving role secretly in the privacy of your home so it isn't possible to find a community of other people in a similar situation.
it's overwhelming and isolating. and when you do start looking for resources on how to take care of yourself or searching for some community where you could vent and feel understood... all you'll find are lists of tips for "here's how to help your loved one start therapy". i know they mean well, but it just reinforces the idea that you were wrong to have been thinking about your own needs and you really just need to be more selfless and more dedicated to supporting your loved ones.