YAY for you Muffin
I can't find much about prawn crackers only the following:
Food cravings may be caused by hormonal changes in pregnancy, which can make some women more or less sensitive to tastes and smells. There is no evidence, however, that a craving indicates a need for any particular nutrient. If you crave pickles, for instance, it does not mean you need salt, and if you crave ice cream, you are not short on calcium. You may simply want the comfort associated with certain types of foods. If your cravings for junk food get out of hand, try to substitute foods that are more nutritious but similar in some way.
If you're looking for something cool and creamy, have ice milk or low-fat frozen yogurt instead of ice cream.
If you're looking for crunch, have baby carrots or unsalted pretzels instead of prawn crackers or potato chips.
If you're looking for a sweet taste, have fresh, frozen, canned or dried fruit instead of candy, cake or cookies.