Pregnancy and weight loss

does anyone else lose weight while pregnant??? I lost over 20 pounds while pregnant with my daughter due to extreme morning sickness. I could only eat Apple slices and French fries with her for almost 6 month's. My OB thought I was dieting with her and now pregnant with my son I'm just 19 weeks today and have lost almost 15 pounds. I haven't had hardly any morning sickness with this pregnancy just a meat aversion for the first 14 weeks but I'm still dropping weight. Is this normal,!? My OB isn't concerned yet but I've only seen him once this pregnancy the other 2 times I've seen a nurse practitioner.