Pumping issues

Cara

I only breastfeed and I started pumping this morning so I can start my little one on some rice cereal for the first time and to mix my breast milk in but I’ve been pumping for 18 minutes and this is all I can get out, my Bub doesn’t have any issues with feedings and he is gaining weight regularly and the doctors and heath nurses don’t see a feeding issue so does anyone know how I can get more milk when I’m pumping?