You won’t stretch your tummy. It takes a prolonged length of time eating excessive volumes of food to do that (think how long you were working on stretching your tummy before surgery). What you may do at this stage is stress or strain your healing tummy & delay your recovery.
Though some do continue to feel hunger after surgery it is not common as most/all of the section of your tummy that produces the hunger hormone is removed. You could be experiencing head hunger - eating for comfort after the stress of the surgery, etc., eating out of habit, craving a texture, food or flavour, etc. At the moment your body is still producing the amount of stomach acid you needed to digest larger volumes of food in your old larger tummy & in reaction to the surgery. Stomach acid can make you think your hungry (hunger pangs). A PPI will reduce the amount of acid in your tummy (via a prescription or over the counter like Pepcid or similar). Also a growling rumbling tummy is usually a sign not of hunger but of your body digesting food. The stretch you felt possibly was just a muscle spasm (your tummy is a muscle).
Usually we aren’t able to eat pudding until we’re on the purée stage about two weeks post surgery & after the liquid only stage. Plans can be very different but check to ensure you can have it. When eating purées, like pudding, I was a teaspoon dipper so only putting food on the tip of the spoon. That way I stretched out the time it took it eat the portion to more like 30minutes & was much like the 5 minutes between sips advice. Also this is when I started, what is still a habit, of asking myself if I really need the next bite or just want it. Listen to your body & go slowly.