Question about weight!

Abbigail • Married and expecting a little boy on May 16th, 2016!! 💙😍 we love him so much already!
Okay, so I know 2 other girls who were/are pregnant. The first girl miscarried at 7 weeks ish (she went to the doctor for bleeding but she had no HCG and no sign of the baby and she never went back for follow up appointments) but she gained enough weight to get one HUGE stretch mark on her upper stomach. She wasn't very thin to begin with but she was filling out a materity shirt already. Another girl (also not very thin to begin with) has gained over 15 pounds and she is 11 weeks. She claimed to started showing at 7 weeks. I am 6 weeks and 2 days, and have lost 3 pounds, no stretch marks, no baby bump. Just a little bit of bloat. I've had only some morning sickness, and keep taking tests to make sure they get darker. Is there something wrong with me? I'm not super thin but I am in decent shape and have a thin waist. I know everyone's body's are different but yeah.