I had a similar problem with my two sibes when I gave them some red meat. They wouldn't eat very much, if anything, and also had really bad wind. They were however drinking and weeing, and when they finally did manage to have a poo, it was very runny.
I too was exceedingly stressed, even though my dog weren't, and as long as he is drinking, I would try and wait it out.
I can't remember how long my two were like this, but I think it was about 24-48 hours.
Hope your boy is feeling better soon.