I never go by the bags... I measure on the bottles, then write it on where you put the date. It is easier to just do that.
I have been pumping for about 4 weeks, mine milk production went the same way yours did, then suddenly I am getting 20oz a day. I don't know why that happened so suddenly, or if it does for most people, hopefully Lenore posts a reply to you soon with the answers for that one. <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
Congratulations !