Family issues / stresses

I'm having a bit of a tough time at home. It's a bit random but my mum has some health problems, nothing too major but she's currently trying to get a hospital operation which is taking a very long time to get passed through. She needs lots of support e.g. driven to work and home everyday by my dad as her mobility is not good. It has definitely put a few stresses on us as she is not able to do many things anymore. My dad has to do almost everything. It has been like this for the last 7 or months so its nothing new. On saturday verything was fine and dad was in a good mood, sunday my dad was in a really bad mood for some reason. He kept really busy around the house and didn't speak to me or my mum all day. When either of us spoke to him we got one word answers and he was very rude and uninterested.He tends to be a bit up and down with moods but generally they pass in a day or so. It's now Tuesday so its been 3 days and he is still the same, he is not speaking to me or my mum and is doing stuff round the house and looking really miserable and angry. I don't know whats wrong but its really annoying me as its making home feel very uncomfortable and when I try to speak to him I get ignored. My mum has been getting upset and crying the past few days because of things happening with her health and the hospital, she cant talk to my dad because of how he is being and so i'm dealing with it all and trying to make her feel happy and better about things even though I am feeling upset myself and stressed. She also said that years ago my dad would get in these moods and it would go on for weeks......I cannot cope with this for weeks! Any advice or words of encouragement please x