Little nervous here towards the end

I had my regular scheduled doctors appointment on Tuesday and it was very informative. First she measured my belly and then looked for her heartbeat. It took her a little bit (Addi was moving around a lot) and when she found it she felt like the placement of the heartbeat was a little lower then it should be. Also she said my belly measured a little bigger then what it should be. So on March 3rd I have another ultrasound. This one will tell me the growth and position of the baby. I think with her heatbeat being lower it might mean she has already started to position her self to slide out of the birth canal. Which being as though I have 5 more weeks left its not that good of an idea for her to do that :) Maybe because my belly is measuring larger then it should I might end up being farther along then originally guessed.
I have no idea. Lots of things are going through my head. You should see the room..... nothing is ready, I haven't even had my family babyshower yet!! I hope she waits till Mommy can organize everything.