Some intestinal upsets create increased motility., as can occur with e-coli.The toxins from the bacterium have been shown to sometimes stimulate excessive contractions in the gut, hence the owner hearing loud gurgling noises. The noise results from gas production . This means the gut is moving but isn't properly processing food.
if he is eating hay that is great , if he is pooping normal that is even better.
I would be concerned that he is getting adequate hydration .Are you giving him sub Q fluids or do you see him drinking fluids? If not you may need to syringe fluids like unflavored pedialyte and/or call your vet and ask about getting sub q fluids for him.
Since he is on an antibiotic he may have a gut bacterial imbalance and need a probiotic like benebac. Can you get that from your vet? I think it would help.
Giving simethicone is great and you can repeat doses about 3-4 times ...
I am unsure but think that valium could slow the gut a little but am not sure about the use of valium as I have never used it.