How much did he weight at birth? How long did it take for him to re-gain his birth weight? Is he on the same percentile as at birth and has suddenly dropped? How big were your other kids....how big are you and his dad?
I agree that 8 lbs. sounds a little light for 2 months, but that really is all dependent on where he started and a lot of other factors.
Once he finishes one side, burp him and put him right back on the same breast before you offer the second side. Alternate which breast you start with. That will help him get as much hindmilk as possible--though dirty diapers would indicate that he is getting at least some. If you are pumping to increase your supply, pump first and nurse second. You can always give him what you've pumped until your supply builds.
I also think you'll notice an improvement now that you've weaned him off the shield. They serve their purpose but can reduce your supply in the long term.
As far as I know, under the best circumstances, a pump will only get about 60% of what is available...so it is good not to judge your supply by what you are getting. Also, if you are only pumping occasionally, your body isn't likely to cooperate.
Just as a note, my daughter was 6lbs. 7oz. at birth (37.5 weeks) and was 12lbs. 4oz. when she was 12 weeks old and was exclusively breastfed. (I, for some reason, can't locate her weigth at 8 weeks).