Feeling huge but told my bump is small

I’m pretty confused! I’m currently 34 weeks. Pre-pregnancy I weighed about 155 or so and now I’m weighing at 200. So I’ve gained 45 pounds or so but I’m still told my bump is small. Granted my baby boy is on the smaller side at 3 pounds 14 ounces at 31 weeks 5 days, where is all this weight coming from? I walk 30 minutes 5 days a week at the minimum. This is my 3rd pregnancy but second to make it this far. All my weight is going straight to my hips and booty and I can’t wear any of my clothes!