Diverticulitis?!

Diverticulitis?

Is it normal for Dr.'s to prescribe antibiotics for diverticulitis?

Yes it is. In fact I've had several bouts of this nasty little disease and my doctor prescribed a combination of two, with repeats, to get on top of it.
Do you know what it is? There are tiny little finger like projections in your intestine and they are where the digested foods get absorbed for the most part. The problem is when these get a blow out, like a stretched part on the side of your intestine, forming a pocket, where food gets trapped, becomes infected and poisons the rest of the intestine, hence the pain and the runs. If let untreated it can cause the bowels to perferate, causing that muck to leak into the abdominal cavity, spreading the infection even further.
To prevent it maintain a healthy weight, exercise regularly, eat a low fat diet, and prevent constipation, which stretches the bowels, and keep well hydrated. Avoid changing to a too high fibre diet too quickly or you could get symptoms anyway. (Too much fibre can be like a rough brush on a sore spot.)