Exclusively pumping. Need advice!!

I have been exclusively pumping for about a month without nursing. I have been doing great with milk production and have been keeping up, but now I have started working (nannying 17mo old twins) and feel like my milk is lowering. I get 4 oz atleast out of each pump session and that's every 3.5-4 hours. But before I was getting up to 5-6 each session and sometimes 5-6 each breast. I'm making just enough to keep up with my baby but some days she eats more then others and I'm scared I won't make enough and I really don't want to stop, what can I do to increase my supply again besides nursing her. (She doesn't latch as well as she did when she was first born. I introduced the bottle to soon.)