Always hungry now that I'm doing a workout regimen?

I'm skinny and trying to gain weight. I'm on P90X (today's my second day), and am following the nutrition guide. I am on Phase 2 Level 3 (3000+ calories), and yet I always feel incredibly hungry after eating what it says to; it just isn't enough. I'm eating more than the guideline says to, yet it is healthful food—no junk. Is it okay to eat outside of the guideline? I'm taking in about 4000+ calories (about 7 meals a day, about 550 calories per meal—one meal every 2.5 hours).