Mum is in a hospice - how do I cope?

I am living with my mum in LOROS hospice as she wants me here and I want to be here for her and love care support her as she says she gets very scared if I wasn’t here and my mum is my world we are so close she has terminal cancer and really suffering Lt is breaking my heart I wish want to tale it from her I would rather have it than my mum .my world is falling apart I am very low but mum needs me so put on brave act as if I don’t I will fall to the floor. My worst fear phobia was anything happening to mum and then our dog who sadly died recently she was therapy to mum and me. I’m struggling and scared .part feels this is some weird nitemare dream world its a coping thing .I don’t know? I’m scared and so so sad there was so much mum and me wanted to do together I’m gutted.so very scared.
Any help appricited. thank you. Tray