S.,
I had breastmilk jaundice too. My baby had jaundice levels that reached 15 when she was a week old, but didn't have to be treated. Then, after a month, I noticed that she was starting to get noticably yellow. At her two month dr appointment, I had her levels checked, and they were at 18. The dr told me it was breastmilk jaundice and that I should put her on formula for a few days. I said NO! There are so many problems with formulas, allergies and links to type 2 diabetes and digestive problems, that I just didn't want to do it. I called my la leche league leader, who said as long as the levels don't get over 25, which they will not reach in breastmilk jaundice, the baby was OK. I had to tell my dr that I was going to disagree with her, which was not comfortable, but I had to do what I thought was best for my baby. Anyway, the yellow lasted another month, but gradually decreased as I fed her a ton and put her in the sunlight as much as I could. By three and a half months, she was not yellow at all, and her levels were in the normal. So, it was a looong process, but the baby was in no danger even though she had high levels, and I never had to stop breastfeeding or supplement with formula.
Good luck to you!