Unfortunately, there is no magic length of time or milestone age when a puppy can be considered fully housetrained and there are many factors that go into how quickly a puppy can be potty trained. Your puppy’s age plays a major role during the initial phase of potty training, as a very young puppy won’t have the muscle control necessary to hold it for long periods of time.
Young puppies can’t hold their bowels & bladders for long. If you come home to find that they’ve had an accident in there it’s quite possible that they can’t hold it that long. Generally puppies can hold their bladder for about one hour per month of age. So your 3 month old pup can probably only hold their bladder for about 3 hours. If you’re going to be away at work for long periods of time see if you can get a neighbor, relative or dog sitter to come over to let your pup out during the day.
If your puppy is not sleeping in her crate or pen, and is out in the house, you must follow her around to know what she is doing: chewing a bone, running circles, getting a drink of water, etc. In fact, don't take your eye off of her! If you cannot watch her continuously, you must put her back into her pen or crate to prevent potty training "mistakes".
Konrad Lorenz, an Austrian scientist who is regarded as developing the foundations of ethological research,[16] further popularised animal behaviorism with his books, Man Meets Dog and King Solomon's Ring.[17] Lorenz stated that there were three essential commands to teach a dog: "lie down" (stay where you are), "basket" (go over there) and "heel" (come with me).[18]
A word of advice – DO NOT use potty pads; use an outdoor potty spot right away, instead. Many people are proponents of potty pads, but they can be counterintuitive at times. Yes, if you train your doggy properly, it will go potty on the potty pad when it’s time to eliminate. What happens when you take the potty pad away, though, and your dog has developed this routine of going on the pad?

A dog learns from interactions it has with its environment.[1] This can be through classical conditioning, where it forms an association between two stimuli; non-associative learning, where its behavior is modified through habituation or sensitisation; and operant conditioning, where it forms an association between an antecedent and its consequence.[2]
In October 2012, Millan appeared on The Alan Titchmarsh Show. Titchmarsh called his methods "cruel" and "unnecessary", citing a video in which, Titchmarsh said, Millan punched a dog in the throat. Millan called it a touch, not a punch. Titchmarsh read out an RSPCA statement saying that "Adverse training techniques which have been seen to be used by Cesar Millan can cause pain and fear for dogs and may worsen their behavioural problems."[38][39] Writing in the British newspaper Metro, features writer, Andrew Williams, described the interview as the first time that Titchmarsh has "deviated from his usual interview strategy – which runs the gamut from mild to wild sycophancy" and described him as "probably the only celeb Millan has failed to win over..."[40]
Operant conditioning (or instrumental conditioning) is a form of learning in which an individual's behavior is modified by its consequences. Two complementary motivations drive instrumental learning: the maximization of positive outcomes and minimization of aversive ones.[39] There are two ways in which behavior is reinforced or strengthened: positive reinforcement occurs when a behavior is strengthened by producing some desirable consequence; negative reinforcement occurs when a behavior is strengthened by avoiding some undesirable consequence. There are two ways in which behavior is decreased or weakened: negative punishment occurs when a behavior is weakened by not producing a reinforcing consequence; and positive punishment occurs when a behavior is weakened by producing a consequence that is a disincentive. In combination, these basic reinforcing and punishing contingencies provide four ways for modifying behavior.[40] Reinforcement increases the relative probability or frequency of the behavior it follows, while punishment decreases the relative probability or frequency of the behaviour it follows.
Millan's work focuses on handling a dog with what he calls "calm-assertive energy".[9] He believes that dog owners should establish their role as calm-assertive pack leaders.[18] According to Millan, dogs have three primary needs:[18] exercise, discipline and affection, in that order.[30] In other words, it is the owner's responsibility to fulfill the dog's energy level needs through challenging exercise; then to provide clearly communicated rules, boundaries and limitations; and finally, to provide affection.[31] According to Millan, a common pitfall for American dog owners is to give a great deal of affection with very little exercise and even less discipline.[31] He encourages owners to understand the effect their own attitudes, internal emotions and physical postures have on a dog's behavior, counseling owners to hold strong posture (i.e., shoulders high and chest forward) and to project energy that is calm-assertive.[16][32]
Be persistent! Make sure the puppy doesn't get the opportunity to pee and poop by using a leash indoors or confining him to a crate when you're out. Depending on the puppies age, pop him outside every 20 - 30 minutes, so there's a greater chance of him toileting outside (by accident at first.) In addition, get rid of any scent markers he's left by peeing or pooping indoors, as these will draw him back to the same spot. This means cleaning the area daily, for 2- 3 weeks after he last pooped there to fully get rid of any lingering odor that the dog can detect.
Every dog needs to learn to walk on a leash. Besides the fact that most areas have leash laws, there will be times when keeping your dog on a leash is for his own safety. Learn how to introduce your dog or puppy to the leash, then teach him how to walk properly on the leash, even beside you on a bike. A loose leash walk teaches your dog not to pull or lunge when on ​the leash, making the experience more enjoyable for both you and your dog.