Exercising not working....thighs and butt are huge!

I'm 18 weeks and I have been working out my legs and butt almost everyday. I don't overeat and I eat fairly healthy without restricting pleasure foods too much. For some reason my butt and thighs want to keep getting wider and wider and more saggy each week!!! What the heck???? Idk what else to do to keep them in shape!!! Anyone else having this problem?? I've only gained 6 lbs so far this pregnancy but by the look of my butt and thighs I look like I gained 20.