I loved nursing my first. And I'm a huge advocate for breastfeeding.
Nursing my second was a nightmare. We kept at it. We kept at it a long time. But had I not been successful with my first, I would have though my body was failing me yet again.
It took her a month to regain her birthweight, and that was with me pumping and supplementing pumped milk because her latch was... well, she'd "latch" but she had no suck. The only reason she didn't do worse in her first week was that my milk came in fine and she did okay on the "spillover".
I had visions of lazy nursing in bed... but ended up with every feed being weigh, nurse, weigh, pump the amount to get to our per-feed goal, feed with bottle (which she also sucked at. Well, no, she didn't suck, that was the problem.) I didn't sleep for months, or if I did, I felt guilty because sleeping often meant missing a feed, and she never, ever asked to nurse.
When she stopped being able to take bottles due to gagging issues, I had to do every single feed by manually expressing into her mouth while hanging my boob over her while she lay on the bed next to me. Did I mention I had excruciating bone pain in my pelvis and sitting hurt?
The doctor said, "Supplement formula if you can't get enough breastmilk." That wasn't an option for me, my gut just said no. Turns out my little girl doesn't tolerate citrates. There are citrates in every brand of formula on the market. The one bottle we ever tried, she vomited.
At five or six months, she started sucking...but she also started clamping down on the nipple. Biting became an every-feed issue, and remained an issue for the next two years. When I weaned her, it was because she'd drawn blood and I couldn't stand it anymore. I had reached a limit where my force of will that kept me from bodily flinging her across the room when she bit or clawed my breast was fracturing, and to keep her safe, we had to wean.
I never, not once after we found out she wasn't gaining, enjoyed nursing her. But I would have hated the tube feeds we'd have had to have done more, so I continued. I don't respond well to pumps, we weighed at each feed so I wouldn't have to pump more than an ounce each time.
I was in some ways blessed in that I learned about breastfeeding from my mother. Mom was given such lousy help with nursing. We had our lips tucked the whole time, and when she told her sister it hurt, her sister said, "Oh, I think it's supposed to hurt." But Mom threw out the doctor's "manual" that gave horrific advice like sterilizing the nipples with alcohol at every feed, and limiting feeds to every 4 hours, and nursed us for 7 - 8 months, at which point she quit because she couldn't stand the looky-loo pulling off the breast distractability that is characteristic of 7 month olds.
I asked her, as she pumped for my sister, "Do you like breastfeeding?"
She said, "No, but I don't do it for me, I do it because it's better for her."
And it is. Don't buy into the myth that weight gain for weight gain's sake alone is the be-all. Some kids are small, and stay small, and they tend to compensate by prioritizing head development. I'd rather see a baby gaining 1/4 ounce per day on breastmilk alone than an ounce per day on formula if they're otherwise healthy and active, because I know that the nutrients in the breastmilk are more "to the point" for the needed growth and development of the brain. My niece was 4 pounds 4 ounces at birth, at term. She's still a tiny little thing, never grew particularly fast, but my god that kid is brilliant. The important thing is that they DO grow, that they have enough energy, that they're awake and alert when they should be awake and alert, not so much x amount of gain per day.
Shiny, on breastmilk alone for her first 6 months, never on formula, is doing far, far better than most of the kids with her exact chromosome problem. The case reports I looked at when she was small agreed... "Kids with this syndrome have profound language issues, some never develop meaningful language at all."
My kid? She doesn't just have language (with delays, but language).... she sings. Beatles songs. She's still special needs. She'll probably never be independent, but I know that she's probably a lot better off than she would have been on formula.
It's okay to set limits about what you're okay with doing with breastfeeding. It's okay to not like it. It's okay to limit it to what you can stand to do. But please don't think that it was a mistake, that you somehow harmed your daughter by doing it.