GemPrincess, no advice really, just empathy. I remember how hard it was with DD, she was born 24th nov, came home on the 20th dec so was in for a few weeks.
It was horrid, every second I wasn't with her I felt guilty, but the one thing I can remember the nurses saying was that she had no clue what was going on, and she wouldn't remember it, so don't feel guilty, Ashton is in the best place and right now, the ones who need you are the bigger children.
The fact that he is off the cpap bodes well, DD was on the full ventilator for about 2weeks and then cpap for another week. Then I went in one day and they said 'Danni-Ella can go home tomorrow' I was so shocked! They said that they didn't want to tell me before incase things got worse, but seriously, you'll get there one day and they'll tell you he can come home, once home it's likely he'll be perfectly fine, with Dd I was petrified and treated her like a china doll, but you'd never know she was born early now.
Easier said than done I know, but try to focus on your bigger DC's and the fact that he will be coming home.
{{{{{{hugs}}}}}}