Cravings (and not for sweets!)

Can somebody explain to me why I'm craving grains? I don't understand it. I mean, I know a craving usually means your diet is deficient in *something*, but I eat plenty of grains. I have a bowl of rice and crackers and bread and cereal frequently throughout the day, but I still crave grains. I generally try to keep it at whole wheat (or as much as possible), but do splurge on my french baguettes. ;)

I have this weird feeling in the pit of my stomach and I don't understand why I'd still be craving something I have so much of. Any doctors out there???

Oy vey, I'm going to go eat some Cheerios now.

Edit: I also wanted to add that I've been having this craving for quite some time now. I can usually dispell the craving by a bowl of cereal, but I just want to get down to the reason why.