Spitting up?

Savannah

A little background info that may help answer my question:

So baby is 9 days old and she is breast fed. She lost 10% of her body weight by day 3 so doctor recommend I nurse her and then pump and give her an oz of my milk. After my milk finally came in I felt as though she was getting enough from me and I don’t give her as many bottles throughout the day. She’s gained back 6 oz as of day 6. Anyway, sometimes she nurses for 15 mins and falls asleep and I try everything to get her back awake to eat more and half the time she doesn’t wake back up so I assume she’s full. I’ll try burping her and she won’t burp but when I go to lay her back she spits up. Do you think she’s spitting up because she’s ate too much or because there’s gas in there under the spit up? I’m trying to decide if she’s getting enough from my breast so that I can stop with the bottles. Definitely don’t want to give her bottles if she’s getting full from the breast.