new puppy

Question
I am desperate!  I am not sure if I am doing anything wrong, but we have a 13 week old Brittany and just recently he has started to pee in the house again.  It seems that it is in the late afternoon when he drinks most of his water.  I can take him out every 10 to 15 minutes!  I leave water out all day and I am home most of the day.  We have a lot of interaction and go on long walks.  Just today, he grab my leg and started moving his pelvis(I just want to be polite and not offend anyone) and beared down.  I quickly got up to not encourage this behaviour.  I know that this is just part of puberty but it seems young.  Could this be the reason for the constant urination?  FYI-he does sleep all night and can hold his pee until we come down at 6am (from 9pm the night before).  I appreciate all the advice you can give me.

Answer
Long walks are great (except for the fact that this is a very young puppy, do not stress his orthopedic development by over exercising him.)  Thirteen weeks is very young for a puppy to wait eight hours overnight. He's just at the age where he can control his urination (barely), but certainly not after playtime, waking from a nap, or having ingested a lot of water (within 30 minutes of same.)  You said: "I can take him out every 10 to 15 minutes"...did you mean you can't?  WHY NOT?  Take him out as often during the day as you can, every 90 minutes is not too much for a puppy this age.  Take him out on leash to the same area every time and walk in small figure eights, encouraging him to urinate with a catch phrase (like, "go pee".)  He'll form a response to the catch phrase after it's been repeated during his urination process over a few weeks and will then understand that this is what you want him to do.  Reward/praise each time he eliminates outdoors and IGNORE his "mistakes" indoors.  Puppies have "accidents", it's part of the process of owning one to reinforce appropriate elimination, rather than expect adult behavior from a very young dog.

"Humping" can be sexual (the result of rising testosterone levels) or behavioral.  If the puppy's testicles are descended, you can have him neutered.