Weight loss while pregnant

Has anyone else experienced constant weight loss while pregnant despite your best efforts to gain weight? I started this pregnancy off at 192 lbs. I'm now 32 weeks and weigh 165. I've been doing everything I can to possibly gain weight. I'm super careful about how active I am, and I feel like I'm always eating. Baby girl is growing just fine, right on target at 4lbs 2oz so far and all her other measurements are good. But I just can't seem to gain any weight. My drs are becoming concerned because we simply can't find a reason for this happening.