Feeling Empty 18weeks 1day! Help!

Mamas quick question I’m 18weeks & 1day & I feel so normal & like my stomach feels empty! It’s a weird feeling but I feel as if there is nothing in my belly. My belly is small so that already makes me feel concerned but lately I feel like my baby isn’t even there!!

I’m a first time mom so that’s why I’m freaking out even more! Any suggestions? Is this normal to feel? Should I try to call my OB’s office? Ughh help!

Ladies please provide your insight!