If your baby was able to nurse substantially when she was ill, then I reckon it's not a supply problem -- I think maybe your breasts became more receptive to baby's suckling and are not as responsive to pumping as before. More nursing/pumping results in a greater milk supply. If you consistently reduce the amount of time nursing or pumping for several days, your overall milk supply will decrease and you can expect to see a decrease during pumping. Keep pumping and nursing the next couple of days and see if the output increases.
If your breasts are engorged in between feeding and expressing milk, then you most likely still have adequate milk supply. Maybe it's a pump problem. If on the other hand, your milk supply is actually decreasing, then there are many things you can do to increase it again. This is a link to my blog: http://pedramusings.blogspot.sg/2015/06/increasing-your-milk-supply.html?m=1
It happen me.. but i feel the suction is different.. i went to service the pump.. yes the say it the motot problem.. after change it ok already.. try to go check the pump fast ..
Is the suction same as previously? Sometime you need change the parts, because there is small tear, hence the effect is not as good as previous.
Check on your pump parts. Maybe your valves are torn since u need to hand express.