I'm truly sorry that your going through this...............it really is the children that suffer the most....................but just keep in mind that there's 2 sides to every story............
1) Don't tell your mom over the phone.............no matter how tempting.....there's nothing she can do about it from there............and she'll only be miserable
2) Consider sitting down and having a "talk" with your dad.............if he is approachable..................there really may be something that didn't even occur to you.................things are not so "black and white"
3) It may not even be your place to "say" anything.............this is an adult problem that you should not be burdened with...............if you must involve yourself.............. tell your dad "if you don't fess up, I'll do it for you".................and when the "talking" starts.............disappear..............
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