Growing body size... Concern

I'm 17 weeks and I'm huge in the butt area(kind of always have been) so with maternity clothes sometime I'm already growing out of them by the time I wear them. I can still wear my bigger shirts but not any of my pants. I feel like my bottom half is growing just as fast as my belly and it's super depressing! Guess I better jump on the treadmill. I have yet to work out my whole pregnancy. Also, I'm gaining about a pound a week so I'm not worried about my weight gain, just my shape if that makes sense.
Any fears or concerns with your changing body?