he amount that comes out when pumping, does not necessarily reflect the amount in your breasts.
Since you are exclusively breastfeeding... is the pumped amount what you are using to estimate how much milk you have in your breasts?
The thing with exclusively breastfeeding is: you go according to your baby. In other words, does he seem satisfied after nursing or does he seem to want more? Does he completely empty your breasts at each feeding? Are you nursing from both breasts per session or just one side? (i nursed using both at each session), does he have enough wet diapers? Is he gaining weight adequately? etc. These are indications to you, on whether or not you have enough milk supply in your breasts.
At this age as well, you should still feed on-demand. For the 1st year, because breatmilk/Formula is the Primary source of nutrition in a baby, not solids and not other liquids. Per our Pediatrician. Also, the quantity you produce, will reflect the amount your baby is nursing... and your body is supposed to adjust to a baby's growth/feedings/amounts/growth-spurts as well. It is supply and demand.
Also, 9 months is a growth-spurt time. So, if you are feeding on-demand... your milk should be keeping up with the increased amounts a baby feeds, at these times.
IF your baby is growing well, gaining weight well, and seems satisfied after each nursing... then you can assume you have enough milk, and he is getting enough. But, if baby is always hungry... then you may want to ask a Lactation Consultant how to gauge your output and his intake needs.
I exclusively breastfed as well... I never gave pumped milk. I hated pumping. But my kids, grew like weeds and gained weight well and consistently and did not seem to lack intake. My Pediatrician, said that this is a good indication that the baby IS getting enough breastmilk. I always fed on-demand... even through a baby's "cluster feeding" spurts... in which they can even need to nurse every hour and frequently. 24/7.
If you are at all concerned about your milk production, ask a Lactation Consultant... and if your Pediatrician in concerned that your baby is not getting enough breastmilk and/or his growth percentiles/weight gain.
Next, if you pump INSTEAD of nursing directly, this will affect your milk production and output... lessening it. Feed by directly nursing whenever possible... this will encourage your milk production best.
All the best,