you should have your first prenatal visit between 10-12 weeks....typically...most doctor like you to miss at least 2 periods before they see you, unless of course you are having bleeding/cramping/other issues. Not to mention, the baby is so small before then, that they would not easily pick a heartbeat up on a doppler until then anyway, so its not really worth an appointment prior to then. When you call, she takes what you say and she determines whether it can wait or not. I would not be concerned at this point. good luck!
If it helps, there are many resources out on the net that gives good information as to what is going on with your body at this time, to help ease your mind. Baby Gaga: Stroller Reviews, Baby Tickers, Pregnancy Calendar (http://www.baby-gaga.com) gives an excellent pregnancy calendar. Also picking up "what to expect when you're expecting" and the "Everything Pregnancy book" will also help.. :)