Help 😔

Can someone please tell me how it works? I'm 29 weeks pregnant and my belly is so tiny comparing to these other moms. I'm a FTM and I have so many people always tell me my baby bump is so tiny although my doctor measures my baby and tells me I'm measuring good for 29 weeks. How is it possible for my baby to be inside me when I'm tiny? Is their enough room for her to move around? Shouldn't I be getting bigger since I'm almost around my 30w? I've always weighed under 110 before I got pregnant I'm 5'2 and I now weight 125 😑 I'm getting tired of hearing these "you're so tiny" comments ☹️ I worry a lot!