No weight gain AT ALL?!?!

Sarah-💙💙👼,due with my 🌈baby in Oct 2018,Team💚

In the beginning of my pregnancy I was 228 lbs, I am 5'7" (bra size 40G though...) In the first 2 months of pregnancy I lost 8 lbs and I was down to 220 lbs,I was NOT sick,just had less appetite. Today I am 18 weeks and I am down to 218 lbs. How is that possible with a round growing belly??? This never happened with my 2 other pregnancies,i always gained the appropriate weight.