Pumping

So I have a 7m old and I was a pumper for the first 5M of her life but I would never get more that .25 ounce every session. I saw a LC and she said I just prolly will never pump enough, I took that in stride and stopped pumping 2 months ago. Now I was also told that every pregnancy you develop more breast tissue for milk production, I am currently pregnant again and I would like to try pumping again. Should I wait until I have the baby to see if I can produce more or is it safe to start now, I heard pumping can put u in preterm labor