When is your supply established?

I'm 4 weeks pp and I've been pumping 8 times a day since about day 3. I've been pumping about 22 ounces a day (up from 12) which seems very low compared to some of the other ladies on this forum. I've tried fenugreek but it was causing stomach trouble for my LO. I've been eatinglactation  cookies and staying hydrated. I'm not sure if I can expect my output to go up anymore at this point. I've noticed that if I pump 2 hours a part I make about the same in 2 sessions as I do in 1 session 4 hours after the last. I'm thinking of just dropping down to 6 pumping sessions a day at 4 hours apart. Has anyone had their output go up past this point so that maybe I should keep up the 8x a day schedule? Or do you think its probably as good as it's going to get?