Pregnant without a cycle ?

So me & my SO had been ttc for over a year & then October of this year I started intentionally losing weight not happy with my pudge but then I developed an eating disorder which caused me to lose over 40lbs in less than two months so with that sudden weight loss, my period stopped. I did not get a period in October or November & my last cycle was September 7th… well fast forward to now… After having so many pregnancy symptoms but negative tests… doctors finally confirmed that I am 8 weeks pregnant which means I got pregnant without my cycle after ttc with a regular cycle for over a year, this is definitely our miracle baby & rainbow baby. I already have a 3 year old son, so this will be my second pregnancy. I have Hyperemesis Gravidarum with this pregnancy so I’m continuing to still lose wight. I went from 185lbs-140lbs (I’m 5’3) & still dropping. Any tips on how to gain weight with Hyperemesis Gravidarum?