This is not uncommon. Around week four your body can start producing its own levels of "sugars" via a process called gluconeogenesis. It is designed to help prevent ketoacidosis and by week four some people are pretty adapted to the new processes.
Add some extra protein for a few days while you get over the hump. You could also play around with the restricted packets. Add one if you haven't used it yet or take it away if you have been using it daily.
You will find the combination that your body responds best too.
Just be aware, week 4 and 5 are common adjustment weeks so, stick it out.
FYI... if you are craving peanut butter, it is often a signal you are needing more protein and fat. Try having a whole egg instead.