Hi S.K. -
Its so scary with your first baby. You just want to do everything right and be sure that the baby os safe! I felt the exact same way.
My first baby was a boy and he was extremely active, but then towards the end of my third trimester - months 8 and 9 - he became a lot less active and it scared M..
Turns out, he was just a big guy in a tiny space. At around 8 lbs. at the time, he was really running out of room!
My advice would be this: as long as you are feeling your baby move intentionally (kicking, or a forceful pushing feeling) I wouldn't worry. You know how sometimes you feel the baby move but its only because you moved first and it was probably just the baby turning due to your change in position - I didn't count those. I watched and waited for the kicks. As long as you feel some activity, I'd try to relax a little.
If your doctors aren't worried and aren't preparing you for an early delivery - I wouldn't worry. You're so close anyway, the poor thing is probably just running out of room in there!
Congratulations!