This is my 4th, and they all have been weaned differently. My oldest was nursed until just over 1 year. She would not eat baby cereal, baby food, pumped breast milk, anything. At just over 1, my mom kept her while I went out of town for a weekend. I came back to a weaned baby, but boy, oh boy, was I SORE that weekend!!
My second was weaned at about 4 months because I worked in an office that was not conducive to pumping. The only place I could pump was in a bathroom stall. I was getting 1-2 ounces, and it just wasn't worth it. I don't recall a huge amount of pain that time.
My third was slowly weaned as we introduced foods. At about 9 months, she decided one day that she was done. She pushed me away and never looked for it again. I don't recall any pain that time because she was down to only a couple of feedings a day.
My fourth is still nursing. Like you, we have had to supplement formula bottles here and there, in large part because the day care was giving her 20 ounces of milk a day when she was 3-4 months old. Had that not happened, I firmly believe I would have had a good back-up supply built up. Since then, I only take the amount that I want her to have in any given day. If it's been rough finding time to pump at work, I sometimes supplement a bottle. And when my husband keeps her 1 day/week, he almost always uses formula because it's easier than heating up the breastmilk. She's been on various solid foods for about the last 2 - 2 1/2 months. However, she is still primarily nursing. I think my husband is ready for her to be weaned, but I'm not. He keeps telling me this is the last one so I'm cherishing this time. I usually only get 6 ounces a day at work, but she is only using 8 at day care so we're managing okay. Also, she still doesn't sleep through the night, and I nurse and give her table food in the evenings. I also make sure she is nursed right before I leave in the morning.
However, I went on a field trip the other day with one of my daughters, and I was not able to pump the whole day. I was so sore by the end of the day. I told her she had to watch the baby for a little bit when we got home so I could pump because I was sure I'd drown her!! I got 9 1/2 ounces at that pumping. Been a LONG time since anything like that. I also had the lumps in one breast, and the slightest movement was making them very tender. I'm hoping your pain is gone by now. For me, I have found it easier pain-wise to wean slowly, but that's not always the easiest emotionally. I'm not looking forward to when I have to wean Katie.