19+5 and have not gained weight, should I be worried?

I never had morning sickness, so throwing up couldn’t be the reason I’m losing weight. I eat enough sometimes too much and not the best food....all I crave is burgers, fries, and potato chips. People tell me “you’ll gain soon, believe me”. I’m morbidly obese but actually want to gain a pound or two. I guess I keep worrying baby must not be growing if I’m not gaining weight.