My pump is killing me... 5 months later.

So this may have to do with my boobs just being sensitive from thrush, but who knows.... anyway, for the last week or so pumping has been really tough!  My nipples and breasts are really sensitive.  I use a Medela PISA.  It's always been somewhat rough at first, but then as the session goes on it feels better.  Lately, I've had to back WAY off on the power and also I switched to 27mm shields.  Maybe I was just being too rough on my boobs all along, and now that I'm back to work they are revolting.  Anyone else have a hard time with the Medela?  Anything I can do to make it more comfortable?  I think I have the right fit for the shields, now that I am experimenting with larger ones.  Are the soft shields helpful?  Or a pain?  What else can I be doing to make pumping more comfortable?  It is weird that I am having all these issues now, at 5 months.  Kind of frustrating!