WORRIED!Fundal height less after weight loss!

I've started a lower carb diet for health during this pregnancy, and to avoid GD.I'm 3 weeks in. I started in the overweight range, and have gained 13lbs at 27.2 weeks.

Yesterday, at my appointment, I'd lost a pound. I actually gained 6lbs after the last appointment and then lost 7 in three weeks NOT trying. FH last month was 26, but this time it was 24! The doctor said she wasn't concerned, but this kind of worries me!! I have noticed baby has started "sideways" laying, but she's usually breech.

Has anyone had this FH loss issue?