The nausea should start to let up soon, have you asked your doctor about meds to help with the nausea? A lot of woman find it easy to eat things like fruit, popsicles, juice, breads/pasta. If your doctor's not concerned, I wouldn't be. If you were a bigger girl before pregnancy it is very normal to lose weight in early pregnancy. I started at 231 and lost to 221, I'm 224 now at 17 weeks pregnant. You don't need the extra calories in the first trimester, just make sure your taking your prenatals, I'm sure everything is fine.
Bland food. Food that doesnt make you feel like you're actually eating. Like jello