Let's look at it from another perspective. Which is healthier for your kid. To have breast milk and a burnt out, exhausted, impatient mom who is not able to be present? Or have formula and a patient, present mom who has energy to look after him and play with him? That's not the calculus for everyone. But it is for a lot of people. It was for me. And I know I don't regret the choice I made at all. Pumping was killing me. I couldn't handle anyone touching me at all (even my son!) and the tiniest noises would make me burst into tears, I had constant migraines, and I wanted to tear my skin off everytime I pumped. So I switched to formula and didn't look back regardless of other people's opinions or my own internalized mom guilt. And my son is huge and strong and healthy and thriving.
If you are willing and able to breastfeed, you could try sticking a hakka on your non-feeding breast to collect any let down (it’s effortless and easy to clean, I wish someone had recommended it to me soooner). Even a small amount of breast milk a day will provide immune benefits and contribute to a healthy gut microbiome, but don’t feel guilty for going down the formula route, babies gotta eat!
You are not a bad mum. Look at any of your grown up friends/family - can you tell how they were fed as a baby? You do what’s best for you and baby, an exhausted mum is not a happy mum, and baby needs a happy mum ❤️ they got the best stuff from you anyway in that first week! I had a similar timed journey, and went fully over to formula, my LG is now 13.5 months and thriving.