So frustrated!! (A rant)

lissbright

My son was born 10 pounds 2 ounces. He's now 12 weeks old and at least 13 pounds (on our scale he is 13pounds 5 ounces but the one at the pediatrician a office is always a little different). I am strictly pumping and have been for a while to get him used to a bottle because I'm going back to work in a few days. I don't know if it's hormones or what but I can't seem to keep up with him and the past 3days I've hardly produced anything and of course he's in a growth spurt and wanting 4oz. Usually I can get 3+ ounces in about 10 minutes. Now I sit at the pump 40 minutes and I'd be lucky if I get 1 1/2 to 2 ounces. I can't sit at a pump all day and I certainly can NOT do 40 min sessions when I'm at work(yes I know legally they have to let me, but that won't stop them from looking for a stupid reason to fire me for taking away from work so much).
Since yesterday I've been pumping what seems like nonstop to help get the supply back up...but god this is so frustrating!! I'm sore from pumping so much, I'm exhausted, he's fussy and hungry all the time. I don't understand-if breastfeeding is natural and the best thing to do, why is it so hard and why do our bodies play games like a drop in supply during a growth spurt lol it's like the universe loves torturing new moms. He's only 12weeks old I can't imagine trying to keep up with his appetite when he's another 2 months older. I'm feeling so discouraged