Sometimes when I feel that way I can trace it back to hidden sugar, but sometimes it's just lagged hunger.
Not sure if you have a journal going yet, but a lot depends on how you're managing your transition. Cut out all grains? All sugar? Most or all starchy veg? Dairy?
Some people have lots of draggy carb flu days and other people have none. It might have just snuck up on you.
And (I just wrote this somewhere else but preparation is everything. Once you get it dialed in for your body the prep will fit into your schedule, but while you're getting the hang of it you absolutely must make sure you have primal food for these times, whether it's your own body screaming for food (feed it! but feed it primal) or dangerous circumstances (whatever these might be for you individually).