Re: Back to work and afraid...
Congrats on your daughter! Stress can definitely impact the amount of milk that you produce - so it's definitely important to stay calm and confident! It sounds like you are making enough milk for her. Babies usually drink about 1 oz to 1.5 oz of milk per hour that they are away from their mothers. 3-4 oz for every 2 hours sounds fine. My 5 month old eats 3 oz every 2 hours.
This link (http://www.kellymom.com/bf/pumping/milkcalc.html) can help you figure out the amount to put into the bottles.
Pumping every 2 hours that you are away from her is a good plan. That is what I also do, and I end up with 12 oz with 4 pump sessions. It's *just* enough to feed DS, who takes 4 bottles of 3 oz each. Don't worry about having extra. You only need to make enough for the next day, and if you want some for emergencies, you could fit in an extra pump session in the middle of the night or on the weekends.
As long as your DD is gaining and having enough wet diapers, you are doing everything right.
Mommy to Alex (born 2/27/11) and Katie (born 3/31/14)