Sounds to me as though you don't have enough fat in your diet. I would check my macros if I was you, to get a feel for how much fat you are actually getting. I find that if I don't get enough fat and veggies I get the munchies. If you need a late night something so you can get to sleep, I find that a tablespoon of grass fed butter will do the trick, or a few berries and cream. Be careful with carbs late as that will tend to get you going instead of sleepy.
Start weight: 225.5 lbs Feb 13 2012. Height: 5'7"
Primal low: 186 lbs
Current weight: 227 lbs
S.T. goals: try thyroid supplementation.
Goal weight: 135 lbs
"I shall be telling this with a sigh somewhere ages and ages hence: Two roads diverged in a wood, and I - I took the one less travelled by, and that has made all the difference." Robert Frost.