First time mom breastfeeding

My baby girl is 1 week & a day old already & we are breastfeeding, everything is going great I couldn't ask for anything better! But she is only eating on one boob at a feeding & it's not for long maybe 10-20 minutes mostly 10 or 15. I try to move her to the other side but she just falls asleep or just doesn't wanna take like she's already full or something. She will go 2-4 hours without eating again. We've also tried many ways to wake her up to keep her going & sometime it works & sometimes she's just so out.  Is this normal? Is she getting enough to hold her over for that long? Any advice on how to get her to keep going? I just wanna feel like I'm doing this right, I don't want to hurt her like if she's not getting enough. Please & thank you !