Fellow Exclusively pumping mommies!

Since my son was born 5-11, I have tried to breast feed. My nipples are to small and had very little success with the breast shield as the milk is extremely hard to get flowing. I started pumping on day 2 as my son was very hungry and my milk still hadn't come in (so I supplemented with formula and gave him what ever I could pump in colostrum between) it took till day 5 till I got my first 2oz of breast gold!! Now I pump every 2-3 hours and was getting 2-3 oz each time. Now, a week plus down the road and instead of producing more milk, I have seen a small decline to about 2-rarely 3oz of milk each time. I'm begining to come to terms that I just may not be able to provide the milk needed for my growing boy. I will not give up! And as long as there is milk in there at all, I will pump and give it to him and supplement with formula when needed. Anyone else experiencing something similar or have any suggestions as to how to produce more? He is currently on breast milk about 90%.