I am so sorry to hear you are going through that
I had lost both of my parents by the time I was 35 years old, so I know exactly how you feel about the fear of something happening to the people you love, and losing them...
Unfortunately it is the way of things, and we need to dig deep to find our inner strength. Have you shared these feelings with your other half? I know it's hard to not feel alone....
Do you have to keep living there? Maybe get your own place, even if it's not far away, so you can still check on your mom daily, but you can also get some separation and time away from the constant stress. You getting sick will not help anything, so you do need to do what is necessary to take care of yourself, as well....