I have been hand expressing colostrum from 28 weeks pregnant (with midwifes approval as was bf DS when I conceived and through early pregnancy).
At first I would fill a 1ml syringe quickly and easily and it increased over time.
Last week (when I was 36 weeks) I hand expressed 10mls in a few minutes, it was pouring out and filled the syringe really quickly, even squirting like real breast milk from one breast. My breasts sort of felt fuller before then emptier afterwards.
Yesterday I tried to express again and I could literally barely get a drop out, and the same today 
This has got me worried for feeding when the baby is born (although obviously I have a really good stash now) has anyone had this happen to them or know why this might have happened?