We had to tether our Saint Bernard to us sometimes, too. He was an awesome dog and not much of a chewer, but he was a bit hard to housebreak. He would just not give you any warning that he had to go, so you had to keep an eye on him. You can imagine what that was like once he started to get bigger! He would even crap in his crate sometimes rather than go to the effort of whining to wake us up- he just did not care! A trainer sounds like a good idea, too, they may be able to give you some tips. My other dog was easy to housebreak, but a chewer, so she had to be watched and the house had to be really puppy proof. They will grow out of it, I promise! It just takes a lot of work when they're still puppies, but if you put that extra effort in you'll literally wake up one morning with an awesome dog. Getting them fixed as soon as they're old enough makes a big difference too- my Saint lost a lot of his stubborness after he was fixed. Good luck and hang in there- I know it's so hard sometimes!