Sorry you are going thru such a rough time. After your mother and sister pass away, take some time to do something special for yourself. Also, get grief councilling if necessary.
My mother has been gone for about 15 & 1/2 years now. My father is in his nineties, and in failing health, so my siblings and I worry that he won't be around much longer. I am fortunate in having interests that help to keep me distracted when I start to feel low. I hope you also have ways to distract yourself when feeling down.
Anyway, you are among friends here at WP.
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If a man does not keep pace with his companions, perhaps it is because he hears a different drummer.
Let him step to the music which he hears, however measured, or far away.--Henry David Thoreau