Work,PUMP, work,BREASTFEEDING

Kimmy • God hear our prayer, see you on JULY 2016 Baby Martinez <3... Sweet peas :)
Hi mommas, 
I will be back at work soon (sucks!) and I'm planning to exclusively give my son breast milk. I was wondering if should pump now and freeze them?!
But how it will work if my soon eat a lot and constant?! Breast feed on one boob and the other pump?! 
It's so frustrating to figure out the best way to do it. PS: my coworker will let me pump at work too, but I'm scared that I will not have enough everyday for him to eat while I'm at work and I don't want to give formula this early.  Thank you :)