Why do I have odd cravings for...?

Dairy as in milk, cheese, yoghurt, ice cream, pickles, avacados, walnuts, peanuts, and last unrelated food item is salmon or any other fish (preferably grilled). And no there is no way that I can be pregnant; I'd have to be having for that to happen don't I? So, if anyone has any scientific explanation as to why I am constantly eating these same things all day (for the past 10 days or so and I'm absolutely not joking) I would appreciate it very much...