Dear Starlite,
I know you have a lot to deal with your own illness on a daily basis. I think your sisters recent death has plunged you further into despair. I've found, that death of a loved one, opens up past wounds and memories - so you're not only dealing with your own illness but all the hurts from the past AND the death of your sister. Are you getting help with grief counseling? All you can do is be very kind and patient with yourself. I hope you feel better soon dear friend.