super fast weight gain

Tiffany • Mommy to two boys (4&2)💙💙.Pregnant with with my baby girl 💗 DD:7/3/17. Two angel babies 😇. Married 💕
So apparently in 6 days I've gained 7lbs! I don't even know how that is possible. I've done great all pregnancy and I definitely don't overeat. I haven't at all. Any reason why I could have gained so much that fast?