Sudden weight loss

So, I struggle with the whole weight gain thing (mentally) with every pregnancy. I had gained 23 lbs as if last week. I'm 29 weeks today, and after weighing, I'm down 4 lbs this week. Should I be concerned? Normally I'd be jumping for joy... It's such a weird process. I don't feel like I've limited my eating habits, nor overworked by body... Other than frequent Braxton Hicks. I have a check up tomorrow, so I plan on asking them, but can someone offer some insight for the time being?