I'm quite new to this site and have only just had a peek into this section, I notice you haven't posted for a while and wondered if you are ok?
I lived a similar existence to your life for two and a half years when my daughter suffered oxygen deprivation at birth (proven medical negligence). She ended up profoundly disabled (CP) and we knew from day 1 that she could die at any time. Bless her, she struggled on for a couple of years but every morning I woke up and wondered if she was still alive. And like you I was up most of the night anyway, checking, tending, crying.. it was and I know for you is, exhausting.
All I can say to you, is to continue as you are. Take one day at a time, be kind to yourself and take all the support you are given. The grieving process has started and it is a long and lonely journey but one day your sun will shine again. My DD died in 2002. It hasn't been easy but now I can look back with pride at how brave and beauriful my DD was and frankly how well I coped. We do, we have to, we are their Mums.
I don't know if you have a husband or partner but one lesson I had to learn was to allow the other to grieve in their own time, in their own way - BUT keep the dialogue with each other open. Its too easy to drift apart in your grief and sometimes very hard to find your way back to each other again. I speak from experience on that one.
I hope you are ok. I hope your DD is well.
Be strong x