Painful letdown

Ha

My son is almost 8 weeks old and I do both breastfeeding and formula, but mostly breastfeeding. I noticed that when he is feeding, my letdown happens a couple minutes after he starts but it is painful even in the breast he isn’t feeding on at the time. Is this because of my large milk supply or is that even normal for it to hurt? If anyone has gone through that and knows ways to make it less painful, I’m open to hearing suggestions! FTM here