Sorry to hear you have had such a rotten day, though it does sound as if there are an awful lot of layers to why you are feeling so upsidedown at the moment, so it is no wonder. I would start by doing as Lcss suggests , and check out your own symptoms, and also allow yourself time to grieve for your gran this must have been a double shock, coming fro your family in such circumstances, so please be gentle with yourself.
Without knowing any of the history, I wonder if part of the reason you can't stop crying is in part due to the fact that your mum and sister coming to your house has thrown your views into disarry- after all whatever they said, they cant really see you as 'dead to them," as their actions speak otherwise.
Hope this week is a better one for you . xx