My aunt who also deals with mental illness among other things helped me to understand. I'm a giver also everyone is put before me and I will run myself ragged trying to make others happy. She says to me the road to wellness is a selfish one. You have to get used to putting yourself first.
It's a hard thing to do but sounds like u need some selfish time too. Just because you leave the family business for a while doesn't mean you can't go back. Also sounds like they need to make a go without you to see just how much they should be appreciating you. I'm just a housewife with 4 kids but two years ago when everyone forgot Mother's Day I really wanted to disappear too. It's like we become that reminder on the fridge that you see so much you start to not see it at all. Good luck!

No matter how small, a positive change deserves to be celebrated!