Hey!
Yes, that long period between meals might have something to do with it. But was one of those meals your lean & green? (Remember that you get 5 Medifast meals plus the lean & green--total 6.) Try to have a meal no less than 2 hours and no more than 3 hours since your last meal, whatever kind it was.
If you are very hungry, remember your allowed snacks! They can really help you get to the next meal.
And make sure you are getting the measured amounts of food in your lean & green. Some peope make the mistake of trying to cut the amounts down--it doesn't work well. (I'm not saying you do this--just trying to come up with tips.)
If you are still headachy and hungry later in the day, you can add an extra shake as an emergency measure.
Good luck!
Jay