Sore again

Its day 2 and yes I am sore again. I did the "core" workout for P90X  yesterday and my core is not that sore maybe I did it wrong, but my legs and back are feeling it! I also took my measurements for arms, thighs, hips, and stomach. I weighed in again and now have a pretty good starting point. I think I need slightly heavier weights then I have been using. I'm thinking 5 pounds. Right now I have 2 pound ones. They are great for somethings but I'm a little stronger in other areas.