Immodium is pretty safe from the small amount of research I did when i looked into it. I rarely take it, but if i had to, I would.
Also, most antibiotics will worsen diarrhea. You might want to consider taking probiotics if not already, such as acidophilus. Make sure you space out your probiotic doses from your antibiotic doses as the antibiotics will kill both the good bacteria (probiotics) and the bad bacteria causing infection.
Thirdly, if you think you might be able to tolerate psyllium husk (ie. Metamucil supplements), or another water soluble fiber, this may also increase the bulk of your stools. Only do so if you are pretty sure you can handle fibrous food items...ie. can you eat at least some cooked veggies? Start on a low dose of it and see what happens maybe?
Exercise may help as mentioned previously...
God Bless