Mine came back in full blast about 16 or 17 weeks because the thought of food made me sick!! It will come back. Even with me eating nearly nothing through the first half of my pregnancy, my little girl is big and healthy. I do take flinstones completes 2x a day though. Prenatals made me bad sick.
At first trimester, no additional calories needed for a baby development, so if you eat normally for you and take vitamins, you shouldn't worry.
Nope its totally normal for first trimester and even early second trimester. Just make sure you make yourself a little snack now and then like a handful of grapes or something.
Trust me it comes back!