Hi! Congratulations on your son!
Are you using a hospital grade pump? If not, definitely rent one, my insurance covered my pump rental (with a little convincing). If you are using a hospital grade pump, I know that some people who used the Medela Lactina pump (which is hospital grade) had issues with milk supply that got better when they switched to a different hospital grade pump, I don't know why that particular pump has such issues. I used a different Medela hospital grade pump which was fine.
I agree with Leigh about consulting with an LC. Also, make sure you keep pumping for a few minutes after your milk stops (I usually tried to pump for 20 minutes). It signals to your body that it needs to make more milk.
Make sure you are eating and drinking enough too. You can order or bake lactation cookies (google it for the recipe or the companies that sell them) that might help too. They have brewers yeast and flax seed meal that are supposed to increase supply. And they are pretty yummy!
Good luck to you! Whatever you can supply for your son is great!