Sick dog... someone help please?

My dog is a half chihuahua half boston terrier. He's about 4 years old. After I took him on a walk he came inside and would not walk up the stairs. He's panting a lot and his stomach is really bloated. he's a very hyper dog normally. his tail is still wagging but he's not being his normal self. It's midnight so I cant take him to a vet. Does anyone have an idea of what might be wrong. he's making moaning sounds but they're short.