Breast milk

Last night I didn't pump from 0300 to 0900, but I did breastfeed him 2 times...he didn't eat much cause he got his first shots yesterday.  I usually pump after I feed him. So I woke up and my boobs felt like they were going to explode! I got a little over 9 oz in 15 min of pumping... Anyone else like this as well? I have 132oz frozen already plus 25 oz in the fridge and the little dude gained 5.5 lbs in 8 weeks...I'm actually afraid of what it's going to feel like when I stop pumping/breastfeeding.