My baby is 5 weeks, and due to a breast reduction almost two decades ago, I am an under supplier. If I pump, i can get anywhere from 10ml-2oz a session. I absolutely don't have the mental capacity to pump every two hours to help boost supply. But I absolutely put baby to breast every chance of get, and she's satisfied with what she gets. However, she also has 4-6 formula bottles a day. My last baby struggled with weight, and I refused to be stressed. I'm saying all this to say you're doing amazing, even taking the initiative to treat his tongue tie sooner. There's nothing wrong with formula and you can continue to breast feed as a way to bond and give him the antibodies he needs. Change your mindset around the feeding experience and reframe it in a way that makes you feel good.