Living with long term illness of daughter

My 15 year old daughter has a long term mysterious illness. We’ve been to see many drs and alternative healers, several of whom think they have the answer but nothing works. Several times my hopes have been raised for a solution and when it doesn’t work I feel crushed. She’s not been to school for a year and a half so has missed all her exams. It seems we’ve come to the end of the road for any medical help now and just have to wait to see if she grows out of it.
I really try hard to stay strong and accepting but I am her carer now and it breaks my heart when I see her so ill. The model I am running.
C: D illness
T: This is too much. I can’t bear it any longer
F: Intense despair.
A:Over eating, Over drinking,
R: Finding it all too much.

I want to get to state where I can cope better on a day to day basis and believe one day she will get better, but there is no evidence of this yet.

Trying to get to have the T as “I am accepting of D’s condition and give her my love and help everyday with joy” just seems so hard when it is so distressing for me as her mother to see her look so unwell. On the surface people think I am coping well but the above model is running underneath.

Please can I have some advice re this.