Third trimester weight loss?

Ellie
I'm 31 weeks and I've lost 6lbs this week of the 30 I've gained. My bump is FLAT! I have no bump but baby is moving...the tiny lump is low on my belly but what the heck? Why the weight loss? I eat like a pig, I don't vomit, the only thing I do is clean my small home. Should I call my doctor or?????