This may end up being a blessing enabling you to be with your mom more right now. I'm sure she doesn't think you are useless. Wasn't it you that made the executive decision to get her to the ER that ended in her finally getting the tests she needed and got her to the better doc?? You just have to redefine useful. Having a paying job isn't everything.

It's funny, I feel useless working. I'm so tired and out of energy that I can't function at home as a mom anymore. I feel like I could be a better mom / wife if I wasn't working. So, I guess it is all about perspective.

You will work it all out in your mind and adjust to your new reality. You may even love it. It is just the initial shock of trying to accept it. You lived through limbo for 16 years, so you must be pretty tough!