Weight gain at 7 weeks already!?

Amanda
So I started out on the thin side to begin with. I'm 5'6 and I weighed 108lbs before getting pregnant. I am now 7 weeks pregnant and have gained 5/6lbs!? Does this seem like Im gaining too fast to you guys? I am currently starting to feel the nausea but I havent actually vomited yet as a side note.