Don't feel bad about calling your doctor with any questions. I just admitted it to the nurses - "I'm going to apologize now - I'm a first time mom and I might be calling a lot!" They laughed and all was fine. It can feel intimidating to call a great deal, but better safe than sorry. If your doc makes you feel strange about it, look for a new practice.
As far as your baby, my daughter was not premature but slept a lot, too. As long as they are eating and creating dirty diapers (you can ask your doc how many to expect a day), then they are fine. I made a pile of the number of diapers she was supposed to use a day and then every time I needed one, took one from that pile. That way, you can easily keep track of how many you actually used that day. It's very important that your baby not become dehydrated because she's not drinking enough. Even though she has been here for 8 weeks, she is only "2 weeks" old as you count from her due date vs. birth date. A 2 week old still sleeps a great deal which is fine as long as she's drinking. But call your doc to feel reassured before your appointment on Friday! Congratulations and best of luck. It gets easier and easier, so hang in there.