Goodness, give yourself a break hon! You're having heart surgery, you've done the absolute best that you can for your baby and you have the rest of his childhood to feed him awesome nutrition!
My eldest daughter had only a few weeks of breast feeding before she shunned it totally so I had to bottle feed her in the end. She's tall, hugely intelligent, fit and disgustingly healthy and at 15, knows it all.
I don't know the forumla myself as I'm in Aus, but soy free sounds like a great start. I'm sure others will jump in.
Good luck with your surgery!