O.k. my sons five days old today..i've been breast feeding him the whole time since he was born.?

my sons five days old today.i have breast fed him since day one..i havent used any formula..i had to start useing formula the nite befour last becouse my breast's was too full for him to latch on to my nipples.they was streatchd out and he could not get latched on..so today i went and got a brest pump..i pumped like two litle bottles,they was like 4 ounce botles..it made 6 ounces altogether..well now my breasts fill empty..he hasent nursed off them today i've just been giving him the milk i pumped out with the breast pump..hes only got one bottle left..so what do i need to do to get more breast milk??i,ve been eating rite..do your breasts just fill up at nite or what..i ned to get more milk..im going back to work after my 6 weeks is up,and i really need to store some milk for him,so he will have something to eat while im at work,and i seem to b put of milk..so what im asking is how do i keep enought milk for him to eat,and to pump for him later??do i need to let him nurse and then pump when hes done or what??