I could barely keep food down in my first trimester, went from 278 to 244 by the time I started my third trimester I weighed 246 because I have had a hard time with foods. Try eating snacks and eat more proteins. I found that certain proteins made me feel less nauseaus while others made it worse.
Could Just be the hormones it was hard for me to eat the entire first trimester and some of the second I went from 112 to 103. Try to do light snacks instead of big meals
Maybe eating too much too fast? Try smaller meals.