Hello D.,
First of all...don't worry. Whenever I was anxious - I would always find it harder to pump and often found that I would pump less.
I pumped and worked and breast fed both my kids for one year until they graduated to cows milk.
Before going back to work, I stock piled frozen milk as you are doing, but I always got more if I pumped WHILE feeding. It's a little awkward till you get used to it, but it worked better for me. Have baby on one side and pump on the other and switch as needed. They always get what they need. I then would pump before I went to bed while baby was asleep.
I typically pumped before work, once in the morning, during my lunch and before I left work and sometimes again before I went to bed. My husband was doing drop off - so would need a bottle to feed baby with first thing in the morning.
Remember when you are away from your baby, you will find you pump a lot more volume.
Both my kids would drink between 16 oz - 20 oz at day care over three feedings depending on what time I picked them up.
I would distribute the milk in three bottles for three feeds about 6 oz each bottle. It always seemed to be enough. They did not always take it all and that was fine. If they had left over or I got there early - then I had a bonus bottle for the next day but I always marked which bottle that was so that it got used first the next day. We were never allowed to leave milk in the daycare fridge over night.
It is quite a committed process and you need to be dedicated if you are going to use breast milk exclusively, but it was definitely worth it for me and my kids.
The important thing is to do what works best for you and them.
If you are stressed, it will probably be harder to pump.
Looking at a picture of your baby while pumping may also help or just thinking about your baby.
Trust your body. You will produce enough for your baby.
I became a little stressed when one day care center, (which I did not chose, by the way), told me that they needed 32 oz on hand at all times! Even if my baby was there for 10 hours which they never were, they would not have drunk that much!
My daycare let me keep some in their freezer in case an extra feed was ever needed.
Also as baby transitions to cereal etc, their needs change.
So bear in mind that solid foods, when the time comes, will also supplement in their own way.
It is definitely worth the investment in a good double electric pump - which I think you have. I actually spent more time setting up, taking down, rinsing the pump and storing the milk than actually pumping at work!
Hope this helps.
S.