pumping fulltime? breastshield sizes?

Hello ladies,
I am a 1st time mom with a 3 week old who had problems latching on and then i had issues with sore nipples and we both never got a hang of it despite spending money on 3 lac consults. I am wondering if there are any moms who have are just pumping. is it possible to pump for a whole yr straight? will your body produced that much milk as the baby grows because right now i get 4oz total. i pump very 3hrs do i have to store in order to feed him later on ( i am a stay home mom so dont have to worry abt returning  ) I want to be able to just pump and feed him. Also i brought medela pump in style any advice on the breastshield sizes. i swear i have brought all of them and can't figure out what size works for me they all rub the nipple on the sides  and leave a little ring followed the instr. on the medela site. the xxl seems to pull more than just my nipple so not going to use that it pulls it inside the funnel by more than 1/2 inch. How much is the pump suppose to pull the nipple inside? Any advice?

[babyscience]

It has been a while for me...so this is going off of memory (my son is almost 3).  He didnt latch either...I tried and tried and he just enjoyed a bottle nipple so much better.  I dont remember what size I got, but I do know it would suck the whole nipple inside....sorta like a cow utter!  I remember that my nipples did hurt for a while and I also got a couple of breast infections, so makes sure you massage every now and then while you are pumping.  I would pump every three hours but I stopped at about 3-4 months, because I had to go back to work.  I have know people who pumped for a year.  To create more milk now...pump often!  You will also have to get up in the middle of the night to pump.  At the beginning, I would pump for the next feeding...then eventually got more and more to store away.  Good luck and just keeping trying!