Sleeping while nursing and low supply

My son (3 weeks old)constantly sleeps while breastfeeding. I try to play with his toes and wake him but he always falls right back asleep. He continues to suck while he sleeps but I'm worried he's not getting it all out because he keeps stopping and going with the sucking. On top of it I only produce one ounce of breast milk and the rest has to be formula. I'm trying to keep him used to breast feeding but it's getting hard with the more he has to eat as he grows. Any advice? Tips? I feed and pump regularly, every 2-3 hours and I'm taking breast feeding suppliments.