2 weeks into breastfeeding and my son is getting enough and my milk is coming through great. but for…

2 weeks into breastfeeding and my son is getting enough and my milk is coming through great. but for some reason I can't pump. when I try and pump it doesn't come out.. anyone else have this problem? I'm wanting to go back to work at 6 weeks but afraid I won't be able to since I can't pump..