I had the same problem at first when I started to pump. I'd get maybe an ounce at first, then at best I'd get 2oz. It's all emotional! It's so crazy what your body can do, and what you need for it to produce the milk. Some tips from my lactation consultant:
Try nursing your son for a bit until your milk lets down, and then try pumping.
As other people mentioned, pump first thing in the morning. It does help.
Try talking to your little guy, or have him within view. Sometimes a picture helps. It'll trigger your hormones to start the letdown.
I wasn't one of those people who couldn't pump with my OH in the room. He'd hold Claire for me, and I'd pump. It helped having her so close. In the end I was able to get 5oz or so, before I stopped BF.
Are there lactation consultants near you? They are a huge help when it comes to stuff like this.