38 wks ultrasound dr said baby is healthy thank God but 6 lbs 2 oz probably due to my stress I think:(

I feel like an awful mama, my now 16 month old was 8 lbs 3.7 oz at birth it was a beautiful pregnancy I ate the best of the best was so happy. This pregnancy I found out as I was entering my second trimester my husband and sister had an inappropriate emotional affair. I tried my best not to be stressed and eat well. But between taking care of my son, the stress, I eat my three meals a day but sometimes on go with my son and not as much food maybe as I did with him and as healthily like I did with my first. I feel like I failed at nourishing my baby because I am so happy Dr said baby is healthy and all his numbers look good but the weight… 6 lbs. I was an 8 lb baby my husband is a huge man, I am tall. I feel like a terrible mama. I know I tried I thought my best but now I feel like I should have tried harder to be stronger and force myself to eat more and More maybe the stress also obviously played a big part but I feel like it’s my fault. Thanks