Teacher mom worries


I am due in January, and I'm sure I'm worrying too much about this now. But do any of my teacher moms out there have any advise for pumping and keeping up milk supple when I go back to work. I will only be able to pump twice a day. And I will not have a opportunity to pump at lunch. So I will go 3 plus hours with out pumping. Please help easy my worries.