Low bmi and pregnant

So when i went to confirm my pregnancy, i was 8 lbs underweight. The dr didnt say anything about my weight. I've always struggled to gain weight. Never had a history of eating disorders, just a fast metabolism that runs in the family😬. Im nervous i could have a miscarriage. Im currently 7 weeks today. I read if you eat lots of fruit and vegetables, it lowers your chances of misscarriage. Also eating chocolate? Has anyone heard of this?

Anyone else had a low bmi when they found out they were pregnant? How was your pregnancy? Also, tips to gaining weight would be much appreciated ladies❤