Hi
Did your team not give you any post op dietary advice.
First of all the not feeling hungry is quite normal and one of the big advantages of the bypass.
Second the most important thing is water consumption, the minimum is two litres not two pints.
With mine during the first four weeks I was only on purée food and then another four weeks on mashed food, also the quantity was no more than a ramekin, you should have been told all this by your team, where did you have your surgery.
Watch out for the yogurts they can be very high in sugars, so might give you dumping syndrome. Make sure you don’t exceed 6 grams per meal.
As for feeling week, that could be de hydration or a lack of Protien, or just your body reacting to the surgery and not getting the normal amount of food it’s used to.
Water and Protien intake is totally under your control, so make sure you boost them, if you cannot get enough protein in a ramekin of food you can take protein drinks.
Hope this has been of help
Paul