Absolutely. I've already had to start a box of postpartum clothes. You're growing a human. Bodies change. I haven't even gained any weight, but I'm a totally different shape than I was 4 months ago. It's all totally normal.
Just keep an eye out for swelling water weight as opposed to regular weight gain
My coworker told me when she was pregnant, she gained 80 lbs and her doctors were never concerned about it, she also started off underweight . I think that’s pretty normal. As long as your doctors aren’t concerned, I wouldn’t be.