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(TMZ) - Mama June and Sugar Bear Thompson are done - separated - because she's convinced he's been cheating on her ... sources tell TMZ.

TMZ reports Mama June has repeatedly caught Sugar Bear trolling on online dating sites. One of them is plentyoffish.com, in which Sugar Bear - with the handle Georgiafighter31054 - says "i love to hunt fish and ride 4wheelers and have a good time.  i luve muddy Boggs and love to ride in the mudd."

Mama June has stopped wearing her wedding ring (technically the couple was never married, but they did have a commitment ceremony).

Sources tell TMZ Mama June plans on taking the kids and moving out - once the latest round of filming "Here Comes Boo Boo" is done ... so she can be closer to her relatives.  She hasn't fully decided on the move.

TMZ is told the producers of the show are scrambling to try and figure out what's next.

June and Sugar Bear tell TMZ, "Sugar Bear and I have decided to take some time apart to figure out some things in our relationship.  We are taking things day by day but regardless of what happens the girls will always be our #1 priority.  We want to thank ya'll for your support."

Photo: Splash News