Try to choose blander food to eat? For my first trimester, I couldn't stand the smell of meat and fish, so I took vegetarian meals and crackers. I also got Diclectin from my gynae to help with the nausea. The nausea will pass for most people after entering the 2nd trimester.
Don't worry too much. At this stage, your body has reserves to fuel the growth of the baby. So even if you don't eat as much, the baby still grows as normal. Try not to stress. No one is perfect, and we're all learning along the way.