Lost a pound?

Brittany • Hello everyone! I am 24 and pregnant with my first baby, my boyfriend and I have now been together for almost 4 years!
So I went in for my 35 week check up and the scale says I lost a pound... Um it's been 3 weeks since I've been there how on earth did I lose and not gain like 5-10 pounds?! Doctor said its nothing to worry about but that's just weird to me..