It does sound like he needs to be checked out by a vet.
Start weighing him daily right now. Cut back on vegetables. Offer lots of hay and make sure they both have a source of water.
- And got the T-shirt
What I'd do is, Lynx suggests, cut back on the vegetables and cut the cucumber completely out for a while. If it would make you feel better, get some infant simethicone and give him 1/4 of an infant dose. And do keep an eye on him, in case he does develop some more sinister symptoms.
It's early and I haven't had much coffee, but I can't see what the new pig would have to do with a swollen stomach.