Should I be pumping at night?

So for example, last night my son (11 weeks old) slept from 7pm-3am, 8 hours. Then from 3:30-7, 3.5 hours. In that time I did not pump or feed. Today my supply seems very low. Should I be pumping every few hours to keep my supply up? He has had this sleeping pattern for a few weeks so it isn't a fluke.