okay, you use a digital scale but honestly, drop the decimal, it means nothing.
so you gained a pound but no notice in size difference. Honestly, I think you gained a little muscle
I've heard of p90x but don't know much about it. Good luck with it, sore the next day is ok but if you're still sore 2 days later, you definately over did it. Also, Stretch out after workouts, even if the program doesn't say to it is the smart thing to do!!!!! A good stretch routine should take 15-20 for your full body!