2nd trimester weight gain

Hello ladies, I am 15 weeks exactly and it seems that I am STARVING all the time. I try to eat decently and get plenty of fruits and vegetables as well as a ton of water. But no matter what I do it seems that the weight just keeps packing on at a higher rate than it should. I started out at 165lbs and I am 5’8 but today on the scale it said 183.... I have been very constipated so that may be part of the issue but I wonder what do you ladies do to help slow down the dreaded weight gain?!?!