Darn. I am so sorry that he had to go back. Please know that lots of prayers are being said daily for your family and that you and that precious boy are in my thoughts.
I am so sorry to hear that you all had to go back into the hospital. Hug that baby for me and I'll just keep praying daily for his recovery to full health.
I know how it feels... I just got back from three weeks in the hospital with my husband. Like you, he got out and less than 24 hours later, was back in with the complications he had. It's rough. There's stress, worry, disappointment, fear...and it's even harder with a child because you can't let them know that anything's bothering you.
If you are religious, please take the time to visit the hospital chapel. There will be someone to cry with -- get the stress out if you need it! just do it if you feel you have to! -- and pray with you and for you.