I just found out my mom might have cancer but she doesn't know that I know.!

I was looking through my mom's text messages because she has contact with her ex-fiance and they've been talking a lot recently so I was just wondering what they were saying. And I saw that he keeps on telling her that he loves her and that they are meant to be together and how he made a mistake a long time ago because they didn't get married. Later on I saw that she sent him a text saying that she went to the doctor's and that she doesn't have enough white blood cells and that she has either HIV, Bone Marrow Cancer or Leukemia. In a different text, she said that she took the HIV test and it was negative.

So she either has cancer or leukemia. i'm really scared and i don't know how to deal with this. i'm in my early teens and my birthday is in 2 days so this isn't a good birthday present. my mom always keeps talking about stuff like what me and my sister would do if she died and now i now why. i keep telling myself that it's not real but i don't know what to do. recently, i was in depression but i am fine now. i also have this crazy imagination and i read fan-fiction(make-belief stories) and i imagine that the character are in my world and i'm speaking to them and the last two days i was worried because i didn't know whether i was living reality or make-belief. i really don't know what to do.