If you're not taking the dog outside to relieve himself, where the heck do you expect him to go?! If you, as a human, didn't have a toilet to go in, where would you have to go?!! I feel sorry for your dog that you're not training him properly. :-(
There are a couple of utube videos showing A big odog going in the toilet! I'd ask them howo they trained their dog under the comments section. BUT that shouldn't replace proper house training. I agree with previous poster .