A few basic concepts to remember, which you maybe following already, but still worth mentioning just in case:
1) For any kind of weight loss, calories consumed must be less than calories burned. So even if you've stepped up your workout frequency, you still may need to eat less volume. In any case, it's worth recording and analysing exactly what you're eating over say a 2 week period and reduce calories consumed if possible.
2) This may seem to contradict point 1 on the surface, but you should eat more often. Meaning, your overall daily volume can stay as it is or be less, but you can have 5-6 meals instead of 3. This will keep your metabolism ticking over instead of slowing because your body perceives your long breaks between meals as a food shortage. Also, eat your largest meal at breakfast and smallest meal last.
3) Water - you've already mentioned that it's what you mainly drink, but just make sure you're having enough. Even if you have water retention issues, reducing water intake will only exacerbate the problem.
4) Alcohol can hinder your body's ability to burn fat, so reduce your intake or go easy on it.
5) Increase the fiber in your diet - for most people the best opportunity to do this is at breakfast. In your case, it might be worth trying having cereal as solid foods can be more effective than liquids in terms of keeping your metabolism active. Try adding nuts to your diet for insoluble fiber.
6) Are you incorporating weights / strength training in your workouts. If not, try it as more lean muscle can improve fat burning, but if you are already doing weights, just be mindful that your body can get confused when trying to build muscle and burn fat at the same time. These are separate processes and therefore it might be worth trying a phased workout plan whereby you focus on muscle building for 4-6 weeks (greater calories) and then after this, spend another 4-6 weeks on burning fat (reduced calories). I've explained this in more detail here...
http://training.fitness.com/nutrition/gain-muscle-lose-weight-52914.html#post431324
7) You could try cycling calories and carbs, meaning you could increase overall calories and/or carbs for 3 or 4 days of the week, then reducing calories/carbs the other days, so long as your weekly calorie/carb intake remains the same. Of course, this will affect energy levels on the down days so it's only something I would do as a last resort.
8) Make sure you're getting enough sleep.
Good luck!