Am craving kiwifruit so have been eating 12-14 everyday. what are the side effects of over eating kiwi fruit?

Probably None: kiwi does have some proteolytic enzymes in it and that much may irritate your stomach, but if it does not than you can probably eat all you want. You might also get some diarrhea.

You're having them..: Diarrhea and loose stools. They are mostly sugar, with a little fat and a little protein, so it FEELS like you can live on them. But they are WAY more fiber than most people are used to eating, aside from the very health-conscious. So it's like a massive colon cleansing. In the long run, though, If you literally LIVED on them, you could become toxic on some vitamins, deficient in others, get sick.