Yes, the best way to know if something is wrong is to check your past bills. My water bill prints a bar chart of the last 12 months, so you can see the period-to-period usage, which is nice. But my water utility also bills us on some kind of oddball cycle, so sometimes you have a whole extra month on one bill, which can really stand out!
If your water usage for one period is much higher than similar periods, and you didn't do anything significant, like fill a pool, then you probably have a leak. One of the most common leaks is a toilet leak in which the toilet is "running." People do not think that adds up to much, but it really does. If your toilet makes a sound like water is running or you have one where you need to "jiggle the handle" to get it to refill properly, then you need to get it fixed. Sometimes the flap valve has just a small leak and you will hear the toilet run water every few minutes and then stop. That's wasting water.
Unfortunately, other kinds of leaks can be harder to detect. I just recently repaired a drip irrigation system in which a tree root had busted a PVC pipe several feet underground. usually drip is very efficient, but in this case, when the irrigation was on, probably hundreds of gallons of water were being released through that underground break. I didn't notice it until plants further down the line started getting dry, and a muddy spot seemed to persist around the area of the tree.
One way to find out if you have a leak is to turn off all the faucets, showers, washing machines. etc. in the house, so you would not expect any water to be flowing, and then go out and watch your meter to see if it is showing any flow. If so, you have a leak. If you can't tell, you may be able to check with your water utility, and they might check it for you.
If you do not have a leak, and your water usage is still high, then the biggest user of water in a household (at least here in the west), is landscaping. You can have the same exact house, with the same exact number of people, and the water usage can be vastly different based solely on how the home is landscaped and irrigated. With the drought we are facing here in CA, everyone should replace some, if not all, of their lawn with drought tolerant plants, and put them on drip irrigation. It's not difficult or expensive, and it looks great and cuts down on maintenance, mowing, fertilizer, weeding, etc., saving water, time, money, and yard waste.