Struggling putting the weight back on

Has anyone else really struggled to put weight back on after pregnancy? I am so grateful that I can eat again and I am eating everything, but the weight just isn’t going back on. I had my baby a year ago and still look completely skeletal. I’ve always been slim (without trying), about 8 and a half stone, but post hypremesis I’m still under 7 and a half and cannot seem to get my weight up at all Any tips?