I just keep gaining and gaining !

I am 27 weeks and didn't start gaining until about 22 weeks . At that point I'd only gained 1 lb. I had a Dr appt Monday and I was up 3 more lbs in 4 weeks . It seems like every day that I weigh I am up a lb. my appetite is no different than it was pre pregnancy, in fact i don't eat as much junk as I used to and no sodas or iced coffee . I don't have GD or preeclampsia and no swelling anywhere (legs, arms, feet, etc .) I just feel like I am constantly gaining now that I'm about to be in my 3rd trimester . I was already overweight pre pregnancy so I don't want to gain too much weight because then I'll have to lose it all after my baby is born . I know someone who only gained 4 lbs her whole pregnancy . I am freaked out !