You can't drink too much water. Your body won't allow it. But it's unlikely youll lose more weight by drinking more water. Water will accelerate the process up to a point. But it's best to drink the amount of water your body requires, and you'll know if you're drinking too little or too much.
Try for a balance of liquid and solids, focusing first on nutrition. It's great you already enjoy water. Most people struggle to get enough to meet the minimum.
As to stretching, that is such a myth. It took years of eating large quantities of food for your stomach to enlarge to the point where it could accommodate your bigger portions. You can't shrink it, either. It's an organ, not a Hefty bag.
This kind of thinking is all part of your eating disorder. And yes, you do have one, as evidenced by your obesity. Focus on REALITY, portion size, frequency of eating, consumption of too much, fat, sugar and carbs, sedentary lifestyle, unrealistic body image, etc.
Don't let your fatbrain distract you from reality. Follow your nutritionist's guidelines and focus on building a healthy life, where your soul chooses joy over self-destruction.
Love yourself more and more people will love you.