It seems that lately when I pump, the flange slips down and the top of my nipple rubs the top of it (and the milk doesn't shoot out because of it; it just sort of oozes). Any ideas on why this is happening? I am using a hands-free bra and it sort of seems like the bra is pushing down too much on it... but I haven't adjusted it since this problem started. I really need both hands to massage the milk out, and this is getting annoying!!