weight??

Kayla • Mommy to a princess 👶🏼👣
I'm almost 20 weeks and I don't know if this is a stupid question or not, but I'm going to ask it no matter what. 
Well, before I got pregnant, since like birth I was a healthy baby no problems, no nothing except mental illnesses which don't really concern my health. But ever since I was growing up, I couldn't gain any weight. In middle school I weighed like 70-80 lbs and 5'0 I felt so fat because of bullying.. I was almost hospitalized for it, but I started eating. Then, when I entered high school, I got my period which made me gain weight but only a few lbs, it wouldn't even make me gain weight really. Now that I'm pregnant I've only gained 4 lbs and it's like I've gained just one lb every time I go to my prenatal appointments or just none at all?? I don't know if this is healthy or not? But I drink lots of water, and I guess you could say I'm healthy?? But I'm worried my baby is not getting the amount of weight she/he needs, or the nutrients of what not.. I don't know I'm super scared..