I had this when I started, and unfortunately it lasted for the first two and a half weeks! Started to think that it was serious, but one day it just stopped...
I was told though that splitting your packs and having 6 half packs a day would help, as its the intense amount of nutrients that can be causing it. Also, make sure you drink a whole glass of water before you shake, and another one after, this usually helps.
Hope it eases up!