not making it to full term?

I'm pretty convinced I'm not going to make it full term. I feel huge. Like I understand that there's literally a baby inside of me and my organs are shifting to make room but I have a short torso, I'm a smaller person (5'1) and I really don't think my body is going to be able to hold this baby in long enough. It just doesn't feel right. And I've been on top of everything, I haven't gained any extra weight. Im 25 weeks and last I checked (last week) I've only gained 16 lbs so far. So what the heck?? Is this normal or am I going to have a premie? Or maybe there's a twin hiding in there somewhere 😂