One other thing, have you checked the valves on the pump to make sure there isn't any tiny cracks. I had some cracks on the medela symphony valves and had to get some new ones. Also are all the bits of the pump dry when you use it. I had a problem with the medela freestyle because I was using the valves without drying them.

I also occassionally use olive oil on my bb when they are sore from pumping.

I'm not sure how long you have been expressing and if you are doing it full time. I'm a full time expresser and noticed when I stopped trying to attach DS to the breast at about 9 weeks I had a big slump in my supply. I ended up having to go on motilium as nothing worked to increase it. This doesn't happen to everyone but it happened to me. I tried raspberry leaf tea, fenugreek and pumping up to 10 times a day (very insane). My supply has been great since going on motilium.