First of all, congratulations on your new baby and congratulations on deciding to try to breastfeed. As you know, breastfeeding is very healthy for the baby and great as well from the mother-baby bond that forms.
The most important ways to stimulate milk production are to continue pumping or nursing. It is great that you are pumping, however if you are able to physically nurse you may find that milk production picks up (nursing is a better stimulator of milk production than pumping). If part of your inability to nurse more frequently is due to problems with the baby latching, then you may want to talk to a lactation consultant to improve your success.
You should also make sure to drink lots of liquids and get lots of rest as able. Dehydration and fatigue are two common reasons for decreasing milk production.
If these strategies do not work for you then you can talk to your OB GYN doctor
or your primary care doctor
. There are a couple of medications that are available that can be used to stimulate milk production when all else fails. The most commonly used one of these medications is Reglan (metoclopramide), which is available by prescription only.