Hi, I'm new so not really sure how this works but looking for a bit of.. I guess, advice/feedback?

So in Nov 2015, I lost my Gran (Dads Mum) to cancerous brain tumours. Then Feb 2016, I lost my Nanna (Mums Mum) to lung cancer. March 2016, my mum was diagnosed with lung cancer. Dec 2016, my mum was then also diagnosed with secondary brain tumours. Feb 2017, we were told the lung cancer is still there but the brain tumours have gone. Absolutely over the moon. 2 weeks ago Mum had a funny 'turn' her left side become totally immobile. Scans revealed the brain tumours are there and bigger than before.

I am now under the illusion that the Feb scan wasn't actually mums because how could they just disappear as well as that and then return in the same place? 

I was working but I've been signed off sick for 4 weeks. 1. Because I'm basically my mums full time carer now and 2. Because I feel I'm meantally and physically exhausted to the point I'm over tired and can't sleep/sleeping too much when I am asleep. 

I literally feel like I'm carrying the whole world on my shoulders but I also feel I'm not doing enough to help my mum. I feel guilty just going out the house for half an hour.