Kotinka has a point. Excessive water consumption can have adverse effects in your body as your kidneys may also not be able to process it.
A woman should roughly drink 2 L of liquid per day (more on a hot day or if you have been exercising). That would include water, other drinks (tea, coffee, soft drinks,...), soup...
Be aware of how much your drink, check the colour of your urine (dark would indicate dehydration), check for other symptoms of dehydration.
Soft drinks are shit for your body. Yes, they are! They can also be addictive.
Replace them with water and you will notice a difference.
Where is this 3L target coming from anyway?
If you reduce your aim to 1.5L / 2L on top of your other drinks, that will be plenty.
Before doing anything drastic (be it diet or water consumption), liaise with your GP.