Drastic weight gain!

Daria • Been married 6 years, have a 7 year old, working on number 2! Yay! Update: Pregnant with di/di girl boy twins! Yay!
Oh....my....gosh! I exploded out of nowhere! I was doing so good I had only gained 35lbs and I haven't changed my diet at all....I've had bad water retention and haven't been moving around as much because of it but 25lbs in a month!? 7lbs in 1 week alone *cries* I still have 2 weeks to go, I don't want to break 300lbs! Is this because of my water weight? I hope so....