Breast milk shortage?

B
Ok so King is 3wks now and I've been exclusively breastfeeding. I FINALLY got a pump today, and I've pumped 3 times. The first time I got about 3oz from one tit, almost a oz from the other. Each time after it was less and less. He just woke up and I didn't have a bottle ready so I put him on my breast and he barely got any out of either breast. I ended up giving him formula for the first time. Anybody else have random shortage? I've been eating regularly all day so I'm sure that's not it