Do what's best for you and your family. I tried hard to breastfeed my first and she just refused to do it, so her doctor told me that babies thrive on formula and/or breast milk, and I wasn't a bad person for giving up. Thank God. Afterwards was happy baby and happy mama.
I have an almost 4 month old son and had the opposite problem, he liked it so much within 24 hours of being born my nipples were a sore, bloody mess. His doctor once again reminded me that if I'm not enjoying it and am stressed, it's not good for anyone and no one would judge me for quitting. (I was crying asking if I could quit at that point because it hurt so much I almost didn't want anyone to put the baby near me.)
Both of my kids are healthy and happy and so am I. There's no wrong way to feed your baby. Fighting over the best way to feed healthy babies good food (formula or breastmilk) is such a first world problem. Do what's best for your family. Obviously, I wouldn't tell everyone you quit because of weight loss, as you can tell from many of the other posts, people are judgey mcjudgersons. I'm sure that's only one of your reasons, and if it's important to you, it's your business and no one else's. Your baby got 4 months of breast milk, that's 4 more months than mine got.
The most important thing is to do what's best for you and your family. You've spent more than a year using your body to do what's best for your baby, if you're ready to have your body back for yourself, that's your business and no one else's.