stopping breastfeeding support

My son is a month old and probably around 4weeks I notice my milk wasn't satisfying him he would eat four ounces then 20 mins later he would want anouther four ounces I really didn't think much of it until it started messing with his sleep so I started supplementing and notice that if I gave him a bottle of my milk I would have to chase the bottle with two more ounces of formula
For him to be full so I was curious and I would give him four once of breast milk one feeding and formula the other and the formula bottle seemed to keep him full longer I don't know Wat was wrong with my milk I just know it was very watery so watery it looked like I mixed it with water so I now feed him formula and he's way more happier but I still feel I let myself down cuz I wanted to breastfeed for at least 9 months