Except for drink soy milk, soup, water ; be relaxed, you should pump more each time (for 60 mins) even if it seems that no more milk is pumping out. Try this method to wait for the second time of "let down" -
Pump 1st side for 15 mins
Change to 2nd side for 15 mins
Change back to 1st side for another 15 mins
Change back to 2nd side for another 15 mins