From my perspective, it is normal to lose sleep as a caregiver who is also a family member, wanting to stay alert and not drop the ball if he needs anything. It might help to deal with whatever is on your mind. If you're always thinking about the things you need to do, write it down on paper. If keeping an eye on him is your main concern, you might think about having some trusted help come in, just to give your mind a break and help you get some quality sleep.
I think it's a mistake for a doctor to give a definite time without explaining it further.