Hi, deb. Antibiotics are very tricky. Sometimes they will cause weight-gain, sometimes not. Mostly they cause water retention. One of the best things you can do is eat 8 ounces of whole-milk, plain yogurt daily during your course of antibiotics and for the week following their completion. Not only will it help to prevent the complication of a yeast infection, it should also help your stomach upset.

Antibiotics not only kill the infection, they also kill the beneficial bacteria in your intestinal tract. That's probably why you're having the stomach upset.

I hope this helps,
;-Deb