New here!

I'm 13 weeks preggo with my 5th and final baby. I have had trouble in the past with my other babies and ended up just bottle feeding them. I'm am DETERMINED this time to exclusively breastfeed. I work full time and will have to return after maternity leave is up. When do I start pumping to start a supply for when I go back to work? I have done some research on the shelf life of stored milk but find mixed answers. What is the general consensus for how long milk can be stored in fridge and freezer?