weight confusion

I can't tell if I've gained weight, lost weight, or stayed the same.  😣
Before I was pregnant my BMI was Balancing right on the boarder of underweight and healthy.  I'm a 19 BMI. 
Our scale is the biggest liar in this house.  It cannot be trusted to remain a square.  
I eat pretty healthy.  But my portions are almost always small, like a child's size.  
I live in Alaska where the winter days are short.  My husband drives our only functional car to work most days. I'm currently not working.  So my days are fairly inactive.  Some days I feel like in gaining weight and I feel like I look bigger but I can't tell if it's lifestyle, baby, or imagination.  Other days I feel like I've lost weight because I'm eating less then my already normal small portions.  
My weight hasn't gained more then 3 pounds for sure. My "bump" looks like a bump if I make it look like a bump but otherwise I can still see abs.  I'm nearing the end of the first trimester.  I have my next appointment in a week and a half so ofcourse ill bring this up but in the mean time any body else have a glacier slow if any.?? 
  The time line says baby should be the size of a plump but I can't imagine anything that size without a greater change to the outside.