Baby weight and Heart

Do any of you ladies remember, or know how much your baby weight when you were 18wks and 5 days? I am currently this far along and I was told today that my baby weights 8oz. Is that good? Dr. said everything is looking good.. But I don't know, I guess my family makes me second guess. And since I have anxiety, and this is my first. I intend to worry a little more... He also said heart is small, but it's normal at this stage because it's still developing, is this true????