water

Can the amount of water you drink stretch your new stomach??

Not usually, your pyloric  valve will release water into your system faster than food that needs to digest. If you are a new patient just stop when you are full...you will know when you over do it. 

You need to get it into your head that your stomach WILL stretch over time.  It will triple or quadruple in size, but a stretch from 2oz to 8oz is nowhere near the football sized stomach you had before.  If you dislike the protein drinks, this stretching is a good thing because you can eat enough real food to fulfill your protein needs...but to answer your question, no.  I would expect extreme discomfort if you drink too much too fast, but no damage.