Breastfeeding

Danielle • Dated my husband since December 2006 and we were married May 2016. Baby boy Henry born June 2nd 2017 👶🏼💙
Is anyone a breastfeeding pro out there? I feed my 10 day old baby on demand and if he doesn't ask for it, I feed every 2-2.5 hours off each breast and then my doctor has me supplement him at the end with 1oz of formula at each feeding, to help him gain back his birth weight. With this, how much should I be pumping to maintain/increase my milk supply? Usually after he eats I can pump a few drops or at the most 1 ounce. But how much should I be doing this a day? 
Also, what foods and how much do you eat per day to help with milk supply?
Our background: My little guy Henry always poops and pees often (6-7 poops a day and 8-9 pees) but he hasn't gained any weight or lost any yet since birth. He as born 2 weeks early. This is why our pediatrician wants us to supplement. 
Thank you in advance! I appreciate it.