pomeranian chihuahua cross

Question
Hi there:
 I recently bought a pomchi.  He is 8 months old and I have had him now for about 1 1/2 weeks.  He is a pretty good dog so far but there are a few things that are starting up I am unsure about.  I was told that he was house trained, but have been finding him peeing on my house plants in my living room, even if I just took him out.  If I tell him no he runs with his tail between his legs and hides.  If I ever try to correct him he pees on the floor or on himself.  I also find while walking him he keeps his tail between his legs (even though I was told he loves walks), he walks great and follows well so I am not sure how to make him more confident.  I also had him at the park the other day (which he usually comes daily to get my kids) he started to exhibit agressive behaviour to my own son as well as tried to nip a little boy.  He has never done this before and I will not tolerate a dog that is agressive.  I was told that he loves kids and I have 4 of them.  He has never shown anything agressive towards them until yesterday at the park (and no other time).  I am home most the time so he seldom kenneled (where I think his previous home he was kenneled most if not all of the day).  He loves attention, cuddles, to play fetch etc and then switches into an agressive, barky dog.  I am not sure how to handle this.  I took him in today to get him neutured and his shots up to date (as I found out they weren't after I purchased him).  Will any of this help or how do I stop this agression, as well as the submissive peeing, and uncontrollable barking (especially when it doesnt happen all the time).  Thank you so much for your time.

Answer
This dog came from either a breeder (too many people looking for quick cash with these 'designer' dogs) or a private home, you didn't mention.  PEOPLE LIE.  NO ONE wants to get rid of a "good" dog unless they're brain dead or subhuman idiots (both of which are abundantly represented in our society unfortunately.)  An eight month old dog that has not been properly socialized and house trained is a problem: your dog is not house trained and he is showing signs of having been abused because of it.  Yelling at a dog because it has urinated inappropriately DOES NOT WORK, it creates a fearful dog, doesn't teach the dog what to DO, and may even provoke aggression when other people inadvertently repeat your behavior (like your children who may yell and run as children will do.)  You have to house train this dog: take him out frequently (every two hours) and praise/food reward every urination: take him to the same location and encourage him ("go pee") before and during his urination, then immediately pop tiny treat into his mouth while praising.  INDOORS put a belly band on him: this is a device used primarily to prevent inappropriate breeding but works for house training also.  It is not abusive, does not hurt, but the dog soon learns it cannot urinate (belly band wraps around body and contains penis).  You can find them here:
http://www.gwlittle.com/cat/Product-Types_357.aspx

Once the dog has begun to understand what "go pee" means and is urinating outdoors easily, maintain the belly band for a couple of weeks longer while slowly extending the outings from every 2 hours to every 3, then 4.  At eight months of age in a home with lots of kids, this puppy may need to urinate frequently: give him at least five outings a day until he matures and then never offer fewer than four a day.  If he's using the house plants, he's at least attempting to approximate lifting leg against greenery, this is actually a good thing.  Be certain to use an enzyme product to clean up where he has urinated indoors.  If you are consistent, in the next month or two he will be close to being house trained, but you will have to be vigilant for about three to six months.  Submissive urination can be a sign that the dog's temperament is not confident (also a sign that he may have been inappropriately disciplined), and this can mean that he becomes frightened/alarmed by events he has not encountered or which startle him.  I have no idea what occurred between the dog and your son or the other child, since you didn't elaborate, but the dog (by following easily with tail between legs) is giving signs that he is NOT SOCIALIZED, was NOT frequently walked, has most likely not experienced children at large who are running and playing, and his aggression (in whatever form) is probably fear based.  You cannot take this dog casually into settings where there are multiple children running and shouting: that is called "flooding" and if the dog is fearful he will attempt to defend himself.  You've had this dog NO TIME AT ALL, you MUST give him time to habituate to your household, take him out and expose him to people/places slowly: observe his body language, if he appears fearful, ask for a trained behavior ("Sit" but use another word) and reward him when he does it, then go forward calmly.  Keep his outings short AND sweet at first, extending time and people, etc., slowly, so he can begin to feel confident.  Use positive reinforcement training to TEACH him behaviors he can offer for reward; go to Dr. Ian Dunbar's site to learn about this:
http://www.youtube.com/watch?v=Hv38ornzzuQ

Children, if older than age ten, can participate in training but they MUST understand how to do it properly and IT MUST BE UNDER YOUR SUPERVISION as an adjunct to YOUR training.  Don't expect "lassie" from an 8 month old puppy that's been dumped on a household with four active children, that won't happen.  Be realistic in your expectations.  Think of it this way: some idiot dumped this innocent animal in your lap, may have lied or exaggerated his qualities, and the animal is presently at a total loss: he doesn't know YOU, he doesn't know WHERE HE IS, he doesn't TRUST YOU, he doesn't know what to do to please you and he's basically TERRIFIED.  Have some patience and have some compassion.  If you feel he's too much for you to manage, call the humane society (NOT the kill shelter) and ask for some assistance to find him an ALL ADULT home.  Meanwhile, look around your area for a positive reinforcement training facility where you can attend a novice obedience class once a week and a credentialed trainer can observe the dog and help you to get him out of his shell and make him more comfortable in your home.  Be sure to attend a class or two before enrolling, be certain there is NO PUNISHMENT or coercion used; if they have a "play group" or other such social interaction, start there.  Your dog needs socialization, he needs to be taught how to please you, he needs to be protected from situations that frighten him until he's more confident, and you need to understand that 6-8 months of age is the PRIME AGE for people to DUMP puppies they've ruined, neglected, or mishandled, and you appear to have received one of these puppies.  Don't let him down again, his life depends on it.