New to pumping, a few questions!!

My LO is 2 weeks old. He doesn't have a problem latching, that seemed to come naturally. I'm nothing more than a little tender so I know he's doing something right. He is still 1.5 oz shy of his birth weight and the pediatrician wants me to introduce the "third breast." Nurse left, nurse right, 2oz of bottle. I'm ok with introducing a bottle. I'm wondering when the best time to pump is. What is a typical pump time and how many ounces should I be getting so that I know I'm producing enough? Is it normal to get more milk from one breast over the other?