BF Sudden Supply Dip

Ladies up until yesterday I always could pump enough milk for my little while I'm at work in two pumps, lately I'm barley getting two ounces out of the entire session I have a freezer stash so I don't need to supplement but what can I do to save my supply!? I have been pumping 4 times at work and when I get home my little one nurses when we are home and seems statisfied.. any suggestions on what is going on? I really want to be able to breastfeed for the first year! I have switched flange twice already this week to see.. any suggestion would be helpful!!