Have you had a regular stomachache recently? You have not figured out the cause or reason for the ache? You may want to see if it is the water that you have been consuming out of the tap. You never know what happens in the ground or wherever the water pipes go because there might be a leak somewhere that causes your water to be slightly contaminated by bacteria. You may also want to stop using the tap water for a while until the problem is solved. Or, another option is, while waiting until the service finds the problem, that you can use water filtration systems that work to purify your tap water.
You want to make sure that the water is very well filtered so that anything that comes along in it is filtered and does not come in to your body after you drink it. Doing a water purification is certainly going to help you stop having the stomachache if the problem came from the water. There are many different types of water purifying devices that you can choose from. Normally, they vary depending on the amount of water that you normally use. You can also connect the tap to the device so that the water is always automatically filtered all the time.