way too thin breastfeeding

I've always been tiny but have always looked healthy. People didn't even know I was pregnant until 8 months and I only gained 25lbs. The day I delivered I was 118. I'm only 5 feet - prior to pregnancy I was bw 92-95lbs. I've been breastfeeding for 8 months and I am now only 82lbs. I do not workout and I try to eat as much as I can but its hard bc I'm so busy. I look sickly - I have no butt and I hate how I look in pictures. I can not gain weight no matter what I eat - Ive cried about this and worry about my health. Is anyone in a similar situation? I had my thryoid tested and yes normal.