breast feeding and pumping for stock pile help!

I really don't know the best way to go about this... I breast feed my new born who is 15 days old... I have pumped mostly once a day if I miss a feeding (husband bottle feeds) or I'm engorged etc. Anyways my friend has a newborn too and she feeds then pumps right after every.single.time! Idk if I can pump every 2-3 hours on top of feeding... It's overwhelming already for me and my baby will fall asleep well after feedings but if I move him off me he cries.. Basically I want to start stock piling my milk before I go to work but i don't know how often I should pump that will not mess up my supply for baby. Also how much milk do i put in each bag? If anyone could share what they do that would be great! Thanks :)