Big Dog Equals Big Puddles

Bella peed inside the house AGAIN. I can't tell you how many times I've woken up to the sound of urine hitting the carpet. It's gotten to the point that when I hear dripping water I fear that it is the sound of Bella peeing inside the house. 

I attached a bell on the back door's doorknob in hopes that she'll hit it with her nose when she needs to go outside. This sounds completely absurd, but she once trained herself to do so in our old home in California. She would walk over to the door, deliberately hit the bell with her nose, and then sit there and wait for me to let her outside. It was a wonderful trick and quite impressive. But this, along with my extensive collection of Disney music, was lost in the move.

Bella is four years old now, and this behavior is really unacceptable. She pees whenever and wherever she wants instead of alerting someone to let her out. The only time she makes any effort to let us know she wants something is when she's hungry, which is just about every hour.

Anyone have any tips on what I can do to correct this behavior? Bella will go to the back door if she wants to go out, but that only works when I am in the living room or kitchen. If I am in my craft room or bedroom, I have no idea that she is waiting for me.

She's currently in time out in the backyard, although that just means that she's standing at the door barking and demanding to be let inside.

I don't like the feeling of warm urine under my hands. Please help!