EBF and Starting to pump

Samantha
How long to pump for? I started to pump a breast at a time for as long as I would normally nurse for but only seem to get 1.5-2 oz. Today i went longer to see if i could get more but it was like almost 10 mins of nothing so i stopped. Baby is gaining weight no problem but not sure why i cant pump more. Need to get her on the bottle for work...any tips?