No weight gain

Natasha

GM ladies. I’m 27 weeks pregnant, yesterday I had my regular ob apt where I was weighed. I was surprised to see that yet again I hadn’t gained any weight (I’ve lost 4lbs total since finding out about the pregnancy in November) My dr. Isn’t concerned since I am overweight to begin with. I mentioned my no weight gain to my sister who just gave birth to her second 2 months ago, and she started saying that it wasn’t normal and unhealthy and I’m “loosing muscle since you’re not gaining weight” My dr. told me a couple months ago that a baby will “feed off your fat” is this true? I’m eating regularly, my bp is normal, I passed my 3hr glucose test, my blood work has been normal, my baby is measuring up to date, I’m just not gaining weight.. Is this harmful to my baby? She now has me worried that I’m doing something wrong? Any insight is helpful!!