i love my mum but..... and now....... and i don't know how i feel........

So, i think my mum is depressed or something like that because her moods change very quickly and over silly things, and it's kind of hard to deal with, but i love her, she's the best mum ever when she's in a good mood, if she's not, its not worth talking to her cause everything you say will be wrong. i love both my parents but they argue a lot, and my mu always asks me who's right, persnally i don't think she should ask me questions like that, but she makes me answer them, and if i say my dads right she gets all upset and says i always take his side, which i don't, and that we all gang up on her and she goes of crying so we all feel bad. anyway it's like you have to watch everything you say to be careful not to upset her and it make life hard but enough about that and she is also very controlling, you have to do everything just the way she wants because she is the parent and i am the child (im 18 years old and have been looking after my self for about 9 years) it's like you have no room to breath cause she's always on top of you making sure you do everything right anyway, recently my mum has had some health probelms and she went to the hospital and everything and they told her they are doing test cause she their is a high chance she is seriously ill and will need lots of medical attention over the next year or so. she hasn't told me this, my dad had to tell me and she doesn't know i know, i wish she told me she might be ill instead of just coming home and saying oh im really sick i need to be in hospital, i would have liked some warning, but anyway i know so thats not the problem, i just don't know how to feel cause she makes my whole life difficult, but i love her and i am upset about it, and i feel bad for getting angry with her about all the stuff she has done to me before