Is it normal to lose weight in pregnancy if I was overweight to begin with?

Unlikely but... This sounds unlikely but if you significantly changed your diet & exercise this may be possible. Please talk to your OB asap . Good luck & congratulations.
No. No, it is not normal to lose weight while being pregnant. It is a great idea to try to be at a more optimal weight before trying to conceive though. A weight gain of at least 15-30 pounds is ideal.