Pregnancy weightloss

Hey ladies. This is my first pregnancy! So help please. So I am 12 weeks pregnant, my first OB appointment was Feb 7th I was 176lbs. On February 17th I was 173lbs I called to let them know I was nauseous, throwing up, and lost 3lbs. They said it could be just me losing water weight and put me on nausea medication. I take it when I feel super nauseous in the morning. There are days that I don’t feel nauseous so I don’t take medication. Then on February 27th I weigh 167lbs. So I lost 6 more pounds, called my OB again to let them know. They are saying that it’s still in the normal range for first trimester. Has anyone ever have this happen before and still have a healthy baby and birth and deliver at a normal week? I’m so scared that me losing weight is going to affect my pregnancy and my baby. Will I start gaining weight once in my second trimester? Help, advice! Thank you.