Telling my son that he came from the pet shop?

honestly its not the same thing. knowing that he came from you is a special feeling and closeness that you need to share with your child and explain how he came to be. you can obviously skip the part, but tell him how you carried him for 9 months and delivered him. its a bond and he needs to know that and as it being the same as santa or the tooth fairy it is different because that's believing in something that is magical and special not a lie not something that actual happened..