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Vanessa Carlton, best known for her hit "A Thousand Miles," has canceled some November tour dates and rescheduled others because of complications stemming from an ectopic pregnancy.

Carlton announced during the first week of her tour that she was pregnant, but as she revealed on Facebook, she learned in mid-October that the pregnancy was ectopic, which means that the embryo was not developing in the uterus, as usual, but instead had settled in her fallopian tube. In her situation, she wrote, the pregnancy was considered non-viable, because the embryo doesn't have room to develop, and the mother is put at high risk for internal bleeding.

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"We caught it relatively early so I was given a shot of Methotrexate, a mild chemotherapy [drug], instead of having surgery," Carlton wrote. "This would hopefully shrink the pregnancy and save my tube." Her management rescheduled some shows, but then, the singer reveals that on October 28, 11 days after receiving the shot, "My tube started to rupture and I was experiencing internal bleeding." She went to the E.R., where she underwent surgery to remove her entire right fallopian tube.

Noting that her left tube and her ovaries are still "perfectly healthy," Carlton added that her doctor theorized that an appendectomy that she had when she was 12 might have produced scar tissue that affected her right tube, causing the ectopic pregnancy. "In case you are a woman with a past appendectomy definitely take note," she wrote.

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But Carlton's troubles didn't end there. The singer then says that she started getting "intense nerve pain" in one of her surgical incisions, and thus canceled her November dates in Vancouver, Bellingham, Portland and Seattle. She plans to perform November 13 in San Francisco.

"I'm so bummed about having to jank up this tour. It started off pretty great. My favorite even," she concluded. "Gimme a couple more days, I'll be ready. Thank you for all your support and understanding through this."