You are doing so good nursing, don't go the formula route!
Suggest changing his diaper when he falls asleep after feeding 7-8 minutes. That will wake him up enough to feed again hopefully for 7-8 minutes more so he is feeding every 2-3 hours instead of every hour. To supplement the breast milk with infant formula, suggest mixing them. Try mixing ¾ breast milk and ¼ infant formulas at first. If he does accept it, then after a week or so, try doing a bottle mix of ½ breast milk, and ½ formulas. If you wish, you can gradually go to a bottle mix of ¼ breast milk and ¾ formulas, then totally to all formula depending on how he accepts it. When you want to wean him off the breast milk you can follow the above also. Try different nipples and the one he accepts the best, only use that one. Hope this helped you.