Drink lots of water. Taking a multivitamin might help, too. Try to get a good night's sleep but don't be surprised if you feel restless or irritable when you try to go to sleep. You can try some herbal tea or hot chocolate or whatever makes you feel soothed and relaxed - as long as it's not alcohol or drugs.
I also found a lot of comfort in reading
Under the Influence that first week. It helped me truly understand why my body was responding the way it was and why I was feeling the things I was feeling. It calmed me down and gave me answers.
Good luck.