Really sorry to hear about your dad and that you've been having a rough time generally Val. I know it can put a huge strain on the people who care for someone both with Parkinsons and now..this other issue...and all the time you worry about the person - quite naturally, without thinking about the impact on you and the other close family.
Grieving is such a difficult thing to predict as well - I remember when my uncle died (he was the closest thing I had to a father when growing up before my mother met my stepdad when I was 12), I avoided going to his house for a couple of years just because if I did, it brought the reality home that he wasn't there any more. One day looking at the pictures of your mum will bring back more good feelings and warm memories than sadness - don't get me wrong, there will ALWAYS be sadness, but they'll become something to cherish rather than avoid. Does that make any sense? But for now, this is all part of going through the loss - the feeling that you were doing ok recently but now have been knocked back to feeling like you did a year ago. Let yourself feel like it - its completely natural. And come here to vent about it if it helps.
Lots and lots of hugs...