i had the exact same problem and know that it can be extremely stressful and frustrating..
my ds dropped almost a pound in the first 3 days (6 lbs 12 oz to 5 lbs 14 oz) and I received horrible advice the first couple weeks which i think affected my supply.
the LC that I saw recommended I do the same...feed for 10 min and then offer the second for the same. if after this time, he was still hungry offer 1 oz of supplement (EBM or formula) and then pump for 10 mins. It is extremely time consuming and I did it with the help of my mom. He did gain 10 ozs that week and was taking about 5-6 ozs of supplement a day.
the 10 min recc seemed strange to me for the reason the pp's have all stated but the LC's opinion was that he was not actively sucking and was not effectively transferring milk even though I would see some swallowing, etc. he was a laid back baby and would bf all day if you'd let him. if he fell asleep at the breast I was to take him off and let him wake up and keep doing this until he was awake.
I will say that this did help him "get down to business" and eat effectively and then I could comfort nurse him as needed. he defintely sucks much better now.
We are still supplementing at 8 weeks and the best thing I have learned in the process now is not to feel gulty/bad that you have to supplement. I think there is a lot of stigma around this issue and it can be hard not to feel like you're letting everyone down. I have tried everything short of prescriptions (acupuncture, herbs, diet, etc.) and I do know not that stress doesn't help the supply issue!
I pumped after every feeding and i can only get 1/2 oz per session on a good day so don't let your amounts stress you out. I just try to pump when he gets a bottle just to keep the stimulation up.
Hang in there! The best thing you can do is feed your baby and be a happy mom! these boards are extremely supportive.
PM me if you have any specific questions..this has been most of what I've been thinking about since he was born!