Im a first time mom as well and before i got pregnant i weighed 93 pounds and i was the same as you in the begining of my pregnancy but it got better after the 16th week and now im 8 months and i eat what i want whenever i want and i weigh 115 the baby is fine and everything is great!
I didn't have an appetite either and was also nausiated when i ate till a little after the 2nd trimester. just make sure u take your prenatal everyday. sometimes i felt so wore down i would take 2 vitamins but ask your doctor first
Dont worry hun you're appetite will increase as you get further along!! and if you are really concerned ask you're dr about drinking ensure or something like that... My dr told me to have two a day when I was in my first trimester bc I couldnt eat anything and lost tons of weight