Originally Answered: Can I stop feeling guilty?
There are so many things that can cause a low-milk supply. Hormone imbalances (like PCOS), weight issues (if your BMI is high), stress, improper stimulus (pump vs baby suckling for instance), medications, pain, and on and on down the list. Some people say 1% of mothers cannot physically breastfeed, the better estimates are 5% and that's not understanding why some mothers have low milk supplies and not counting them in that count. You're going above and beyond, and you're doing fine. PCOS does typically come from your father's side, and your grandmother having it, your father passing it onto you, does fit the bill. Some women with PCOS actually make too much milk, but the majority have the hormone issues and make very little or dry up by 3 months.
You shouldn't feel guilty. Even if you chose to formula feed because of some other reason, you shouldn't feel guilty. Your baby is healthy, happy, and strong. The formula fed babies in my family are as healthy as the breastfed ones. I was breastfed and have allergies, asthma, and a plethora of problems they say are caused by formula. The fact is, we know that it's a correlation, not a causation, and formula is not poison.
I had a similar experience. Before my daughter was born I planned on donating milk. My grandmother was a wet-nurse, my mother donated, I wanted to do the same. We had a good latch, and 3 days after birth she had to be hospitalized with jaundice, and infection, and dehydrated. They had 2 lactation consultants look at me, then an expert came in from 2 hours away, took a look at me, measured my chest and said that I was the reason formula was invented, that my breasts were deformed, and I MIGHT be able to breastfeed a baby after I've had 5. Pumping never worked, so I had to hand-express, and I gave her that in a little cup so that it was easier to get the breastmilk than the bottle formula. After a month or so she latched on again, but would drain me and then need formula. I've been told not to even bother trying with this next one, but I will. A mouthful is still a benefit.
But if someone looks at me and says "You could have breastfed" or "don't you know that formula causes all the sicknesses and diseases?" or something else then I want to punch them in the mouth. They don't know how I sat there and thought she'd be better off with another mother, how my husband had to take over everything, the depression and pain from having to let go of that.