breastfeeding HELP

Rae
I know you're not suppose to pump before birth. I was just trying it out for a minute. Here is my question:  
Well when I squeeze my nipples, colostrum comes out...but when I went to try out my pump today, nothing came out, not even colostrum. I'm 22 days away from having my daughter. Is this a sign I won't be able to BF? Why would colostrum come out when I squeeze by hand but nothing when I pump?