Levi Johnston: Bristol Palin got pregnant to get back at mom

Levi Johnston writes in his upcoming book that his ex-girlfriend Bristol Palin was so angry about her mother's pregnancy with son Trig that she wanted to get pregnant, too.Johnston says when Bristol found out her mother, former Alaska Gov. Sarah Palin, was expecting a baby she responded she should be having a baby, not her mother. He says she told him in March 2008, "Let's get pregnant."His book,