Gerd or spit up?

Shakaree • 23, one daughter, one angel baby and our rainbow is due 6/21/2015
I'm calling the pedi tomorrow but it's Sunday. 
My daughter is awesome at breastfeeding and is 3 weeks old today recently about two days ago she has been having bigger spit ups. At the doctor last Monday she has been gaining weight  just fine but now I'm worried she may have gerd but I'm not sure if it's normal spit ups.
I burp her after every feed and even then she may still sometimes spit up. She hasn't been feeding any differently she eats every 2-3 hours still, she's not a fussy girl at all and even when she spits up she doesn't make it seem like she's in pain but after a 20 minute feed and burp she spits up 2-3 times and sometimes it feels like so much (not to mention so much laundry) 
Please I'm asking for advice and whether I should be super worried or not thank you!