What can you tell me about intestinal bacterial imbalance and how it relates to diet?

I will be asking my doctor about this, so you don’t need to tell me to. I wanted other opinions, however, as I feel doctors are often a bit close-minded about diet’s effect on disease.

I have just started a course of antibiotics. I’m only about a day in, and already I have seen an enormous difference in my digestive health. Antibiotics commonly upset people’s guts, but these have had quite the opposite effect on me.

It has me wondering. If antibiotics are making me more regular, wouldn’t that seem to imply that I had some kind of bacterial imbalance to start with? Can diet contribute to this? I eat a lot of carbohydrates because people with my condition are often helped by eating carbs. Now I’m wondering if that’s a mistake.

A long time ago I read that carbs make great food for certain harmful bacteria in the gut. I learned about the specific carbohydrate diet, in which one refrains from eating any carbs whatsoever. I absolutely could not live on a diet like that, but might it help to at least reduce my carb and sugar intake?

As many of you know, I have a long history of digestive disease which adds many layers of complexity to the story. I don’t expect anyone to have knowledge about any of that, so feel free to answer as though I were a “normal” person and just tell me what you know.

Thanks.