Poorly Dad

Dad has advanced prostate cancer, no further treatment, he regularly gets infections and has just beat sepsis again and is now home. Drs are doing a full body bone scan in near future, X-ray showed shadows.  Dad is in a lot of pain and uncomfortable most of time, very sleepy and tired.  Mum also has difficulties with mobility and gets confused.  

I am finding it all really hard to deal with, each time I see him, I think it's the last time, so scared of loosing him.  Panic each time phone goes, tearful, and have less and less tolerance for others.  I worry about how they manage round the house, shopping, cleaning etc.  Tried to set things up such as cleaner etc but will not have it. Mum has refused help from various services.   (I live 3 hour drive away and work full time). I have been visiting most weekends to do cleaning, shopping etc but am exhausted, feel guilty that I cannot do more for them, feel guilty for not being home and doing own housework etc  

don't really know why I'm posting cause there are no answers, I just don't know how to manage situations or control how I feel, rest of the family appear to be coping much better