If you are concerned about how much your little one is getting, your best bet it to let her nurse on demand. Don't watch the clock. Offer whenever she seems fussy. If you are currently having problems with weight gain, you may need to wake her during the night. If not, though, let her sleep! Some babies do sleep this long at this age. Let her!
One reason doctors can be so quick to prescribe supplements and switching to formula is because they can regulate and monitor formula. You can't measure breastfed nutrition -- and it drives them crazy! It's a little fact worth keeping in mind.
Watch for the signs Darryl posted (enough wet diapers, signs of growth and well-being). These are the important signs of well-being you need to know and watch for; breastmilk ounces pumped and/or consumed is not what you need to know. Sometimes babies do need a little extra help at the beginning. But if all is well now, relax and let your worries go! It's sooo hard to do, I know, but it's much harder on both of you if you are anxious and always counting ounces and minutes and bottles and pumpings. I used to obsess endlessly with my first baby, especially at times when things didn't seem just perfectly on target with what "they" said should be happening. In the end, nature's system did the job.
Your body knew how to conceive, grow and produce your beautiful daughter. It knows how to feed her, too. If you see signs that your daughter is healthy and thriving, there's no reason to worry yourself about supplementing and pumping and waking and measuring.
You can do it!