Emergency?

My bunny was alright and suddenly around 3 hours after feeding him his usual dinner of pellets and hay, he started lying in his litterbox and not eating his veggies. I opened his pen door and he came out and walked like he was constipated. He is now sitting outside, sort of shivering a lot.
Could this be GI Stasis?!?! How long does it take for bunnies to eat and poop?
He eats a lot of hay so GI Stasis was never a big worry for me.
PLEASE HELP, IT'S 1AM AND NOTHING IS OPEN.

Also he's an indoor bunny and he didn't eat anything rabbits aren't supposed to.

Is he still eating?

The best thing you can do is syringe fluids into him. I'm not sure what size he is but 15ml is a tablespoon and I would do at least that much and then give him 10 ml more every hour. If he doesn't start eating in 8 hrs then take him to the vet.

The reason I say to syringe fluids is that many believe stasis and gut slowdowns happen in part because the gut is dehydrated. They also have found that blockages are usually very dry masses and around the blockage the intestines are usually dehydrated as well. Fluids help soften the dry mass blockage so it can move through. A dehydrated gut can not move food through the intestines so hydration is a must. Also, if there is a blockage or partial blockage you are not supposed to force foods, but fluids can help and won't add to the blockage.