My terminally sick mum and I

Hi, 

I'm a 34 year old man, and having spent most of my life living overseas and focusing on my career. I returned to the U.K. a few years ago to spend time with my family and friends, I grew up here.

My mother who lives by herself, my brother moved out who is older and had stage 3 testicular cancer, and my dad lives nearby as my parents are separated. 
April last year She was diagnosised with a rare cancer and told she had months to live. Since the day of diagnosis I moved in. I've been on and off work due to freelance and also wanting to be there for the trial treatments, appointments and so on. She is seeming to get better and her case is in unknown waters as it's so rare and treatment is so new. Since she's been getting her health back and returning to the day to day she knows, I haven't really picked up work again. I'm still freelancing but the main issue is we keep arguing, about small things. And I'm finding myself getting angry at the idle things that don't matter. And I'm unsure why? 

I feel like I've put my life on hold and I'm not really going anywhere and keep feeling guilty for having that feeling, and then I lash out or she gets short with me: and it ends in an argument. I don't want to move out until the cancer treatment is resolved and obviously I don't want to put any added stress on her. 

I'm still the only one going to all appointments and procedures with her but I feel like a carer part of the time and other times I feel like I've reverted back to an angry teenager. 

It's been a long journey full of blue light a&e trips and keeping in hospital for weeks, 3 different trials and it looks like we are getting somewhere. 

im just personally hating myself for having these arguments and being pent up. 

,D