I started using a breast pump a couple of weeks ago to so I could feed baby from the bottle when I was in public. At first I was able to pump a full 3 or 4 oz. in between feeding him. The past week or so When I pump I can only get 2 oz in between feedings. I have tried drinking more water, looking at a picture of my baby to help with letdown but these don't seem to be working. Any other suggestions?