We have been having trouble w BF, long story, and have been trying different slow flow nipples a pumped milk and formula. The latest we tried were playtex drop ins. He "nursed" for 15 mins and nothing came out. Literally nothing. DH held the bottle upside down, pressed on the liner and squeezed the nipple and nothing came out. Whats up? We also tried Breastflow but he could never pull the milk out. Are we doing aomething wrong or is just his latch??