Breastfeeding

I want to breastfeed my son but he was born at 23 weeks. He is drinking my milk now, however I decided to go back to work until he is home from the hospital. Between the hospital, work and planning for the wedding; I find myself pumping less. I am down to pumping about 3 to 4 times a day. I dont want to give up so soon especially since I have had the chance to really breastfeed. What can I do to help keep the milk flow without staying up at night to make up for missed pump times?