my 2 year old dog

Question
hi i have a 2 year old bull terrier that uses my home as his bathroom sometimes he goes out side then for some unknown reson he started doing his buisness inside im his 3rd owner from a pup ive tryed telling him his a good boy when he goes outside and reward him and telling him off when he is bad i dont want to be one of his old owners that gave up on him and pass him on apart from that he is a really good dog and really good with our baby boy  

Answer
Kieth,   Terriers have more understanding than most dogs....But let me give you house breaking psych first.   When dogs are born a they have a natural instinct to keep their den clean...When dogs have to go at 3 weeks old, they will try and walk away from their bedding and go to the bathroom.  At 5 weeks they try to walk farther to go to the bathroom.  As their bladder control increases and their strength increases, they hold it longer and walk further away from their den/bed.  when you get a dog these days someone might have tried to crate train him, and left him too long in a crate where as he was forced to go to the bathroom in his den/bed.  So all instincts are down the tubes.   So you have to reteach him to be clean.  The best way to do this is confining him to a expen or a room...expen is better if you can get one.   You put his bed and food on one end and leave about six inches and paper or puppy pad the rest of the pen.  What you are looking for is to get him to know the difference between bed/den and where he should pee/poop.  Watch where he goes each day and see if he starts to pick a favorite area of the papers/pads.   After a week,  pick up one of the pads, and leave the rest.   If he goes on the pads, this is a good sign......If you have used an expen, keep it by a door that you use to take him out...work the papers toward the door....While you are doing this you are still taking him out as often as possible.   If you want him in a room with you, he must be on leash attached to your belt so you can immediately correct him and run him outside.  Also when he goes outside give the action a name, like "good potty"   when he knows what the word potty means you can also tell him  "no potty"  right??????
Now remember the den scenario,  he will keep his area clean...what happens when he does that and you let him in  a new room????  he thinks it is ok for him to go to the bathroom  there.  This is the biggest mistake dog owners make, they think that when  a dog is housebroken in the kitchen he understands that he shouldn't go in any other rooms.  They don't think that way... They think from the den/bed outward.
Now that you understand the thinking, you should be able to take this and apply it to your dog/
Another thing, go to Petedge.com and buy him a belly belt, so that if he has an accident, he will get himself wet.  This also a deterrent.
Nancy