Pumping for Preemie

My son was born yesterday at 30 weeks. I am going to be breast feeding and pumping until he's able to feed. I was told that it would take a little longer for my milk to come in. I'm getting so frustrated because I'm pumping every 3 hours as the lactation consultant told me to do, but I'm only getting a few drops of colostrum each time. Is there anything I can do to speed up my milk coming in? I have 2 other children, but I didn't breast feed either of them so I'm completely new to this!