Pumping???

Courtney
So I'm only 22 weeks with my first and I'm lactating. My Ob wants me to start pumping already, but everything I've read has said that it could cause preterm labor. I don't want to force our little guy out before he's ready, so I was wondering what experience anyone else has had with this? I already have an appointment with a new Ob to get second opinion, but I don't want to mess anything up.