I Have Often Had Pain In The Stomach During Night

I have often had pain in the stomach during night and after vomiting I do get the relief. Now I am travelling Vietnam and had to eat outside food sometimes. So I had pain today morning when I woke up after that I has watery stool. Now I just took fruits. I know I have to drink bottled water and packed food. Can I take of ofloxacin and ornidazole combination and loperamide along with it. Just one dose. Whenever mild pain in stomach is there, then pain in back also begin. Help me out.
Thank you