I'm so sorry you are having to deal with this
we lost our Buddy 2 months ago - he was loved beyond words - unfortunately in our case, we waited too long to say goodbye - all I can say is I will never wait again - it was not a pretty thing at the end - I will never put an animal through that - ever -
it is soooooo hard to let go - we just want one more hour, day, minute................
my advice is to do it sooner than later -