Your question about having salt cravings while you are pregnant raises an interesting point: are food cravings in pregnancy due to addiction or hormones alone?
There is nothing wrong with eating limes in moderation. There is plenty of Vitamin C. However too many limes means that you may not be eating other foods that are essential for your health and your new baby. Same with salt - in moderation. Eating too much salt will cause you to retain water. There has also been some suggestion that salt alone can be addictive.
I am inclined to think that you are experiencing the unusual cravings that occur with pregnancy. Pregnancy is a time of hormones gone wild: the increases in estrogen, progesterone and human chorionic gonadotropin lead to insomnia, mood disturbances and strange food cravings. At the very least, the pregnant woman have abnormal taste and smell perception, which leads to the intense desire for some foods and aversion to others. Cravings for sweet or salty foods are very typical.
Having abnormal food cravings in pregnancy is very normal: one South African study showed that up to 84% of pregnant women have some kind of food craving. It does not mean you are a food addict if you are wolfing down limes or salt uncontrollably. It is an example of how hormones can strongly dictate appetite. Typical foods that pregnant (and premenstrual) women share are chocolate, pizza, cheese, even ice, and in some cases mud or dirt or cigarette butts. These cravings, which can be completely new to a women’s usual diet occur most often in the first trimester.
I would suggest that you try to moderate your salt and lime intake - and be sure that you are eating other nutritious food as well. You may want to ask the expert in the forum for obstetrics the same question for more information.