I went through a similar thing with our water bill a few years ago -- the breaking point was when we'd been on vacation for a month, and the water bill came to a new personal high. I went and shut off the water at the meter, and started Googling how to find a leak. Meanwhile my neighbor knocks on the door, asking if I knew why his water had been cut off. When I told the backstory about our high water bill, he was like, "what are you talking about? My house has twice as many people as yours, and our water bill is practically nothing."
Long story short: we'd been paying our neighbor's bill for three years while economizing like nobody's business; he'd been paying ours, while thinking that water was basically free.
Advice: learn to read your meter, make sure it's actually yours.