How much is too much milk for a 6 weeks old?

All depends on the kid...my son was born at 9lbs 10 oz and ate like you are describing, never liked the pacifer...he was on a mix of formula and milk, but it seems as though it was endless eating. I worried about the amount he was eating all the time. He also gained weight like a madman, the doctor was never worried, he just told us he was going to be a big kid and had a lot of growth spurts. He is now 32 months 43 inches tall and 45 lbs. and is still a voracious, yet very healthy eater. He is predicted to be between 6'7'' and 6'10'' and has growth spurts very often. His hunger waxes and wains and there are period that he will eat very little and then periods where he can eat all day. Like I said, it all just depends on the kid, your boy could just be one of the lucky ones that may be a basketball or football player someday! If your doctor is not concerned I wouldn't stress out too much, just follow the docs suggestions and enjoy your big, healthy boy. Good luck!