Kate Gosselin shares details about her 12-year-old son Collin's living situation after her ex-husband, Jon Gosselin, told ET that he hasn't seen his son in over a year and a half.

In August, Kate said that she had enrolled Collin -- one of the divorced couple's eight children -- in a program away from home to help him cope with "special needs." In an interview with "Good Morning America" on Monday, Kate says she didn't "even really have a choice" in the matter.

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"It was on the advice of the doctors and it had to happen. He is plotting along and we are too, the "Kate Plus 8" star says. "It definitely was necessary, and I'll go to the ends of the earth for the best for each of them. This was the best thing I can do for him right now and that comforts me."

Kate adds, "There is contact [with Collin] but it's not the same as being at home."

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Kate was also asked about reports that her son told school staffers that he was being abused by his mother, which allegedly led to child services opening up an investigation. "I'm in the public eye," she responds. "I've been investigated many times."

As for Jon claiming that he does not know where his son is living, Kate explains, "We are both court ordered not to speak about the care and custody of our children in detail. I've known all along where [Collin] is, but the world doesn't know, and I'll leave it at that."

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According to Jon, Kate told him that his son is "in a special school for special needs kids with behavioral problems," but he claims that law enforcement officials have told him otherwise. The 39-year-old former reality star said that he's now planning to go to court in hopes to get his ex-wife to tell him the whereabouts of Collin.

"I've lost track of how many times he's said that," Kate said of Jon threatening legal action. "I'm really focused less on what Jon has to say. I don't really pay attention, to be honest."