I have been pumping most nights with the medela swing to build a supply of EBM for when I go to work etc. I started work a week ago and my period came back on Monday. This week I haven't been able to express very much at all and I had put it down to work and my period. Now though I am wondering if it is my pump, the nipple doesn't seem to be getting drawn out much and today I barely covered the bottom of the bottle when I would of expected to get quite a bit. I checked all the bits are well attached, I wonder if the white valve bit can get worn out? I'm just waiting for my avent manual to cool down and then I will try that one. Any ideas?